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(±)-erythro-Isoleucine is a flavouring ingredient, dietary supplement, and a nutrient. Branched-chain amino acids (BCAA) are essential amino acids whose carbon structure is marked by a branch point. These three amino acids are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. BCAA denotes valine, isoleucine, and leucine which are branched chain essential amino acids. Despite their structural similarities, the branched amino acids have different metabolic routes, with valine going solely to carbohydrates, leucine solely to fats, and isoleucine to both. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg, and 16 mg/kg of valine, leucine, and isoleucine respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. BCAA are decreased in patients with liver disease such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia, or portacaval shunt. Aromatic amino acids (AAA)-tyrosine, tryptophan, and phenylalanine (as well as methionine) are increased in these conditions. Valine, in particular, has been established as a useful supplemental therapy to the ailing liver. All the BCAA probably compete with AAA for absorption into the brain. Supplemental BCAA with vitamin B6 and zinc help normalize the BCAA:AAA ratio. The BCAA are not without side effects. Leucine alone, for example, exacerbates pellagra and can cause psychosis in pellagra patients by increasing excretion of niacin in the urine. Leucine may lower brain serotonin and dopamine. The ratio of leucine to other BCAA is greatest in pork, where leucine is 7 to 8 g and the other BCAA together are only 3 to 4 g (http://www.dcnutrition.com).

Isoleucine (Ile) or L-isoleucine is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-isolecuine is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Isoleucine is found in all organisms ranging from bacteria to plants to animals. It is classified as a non-polar, uncharged (at physiological pH) aliphatic amino acid. Isoleucine is an essential amino acid in humans, meaning the body cannot synthesize it and that it must be obtained from the diet. In plants and microorganisms, isoleucine is synthesized starting from pyruvate and alpha-ketobutyrate. Isoleucine is classified as a branched chain amino acid (BCAA). BCAAs include three amino acids: isoleucine, leucine and valine. They are alpha amino acids whose carbon structure is marked by a beta branch point. Despite their structural similarities, BCAAs have different metabolic routes, with valine going solely to carbohydrates (glucogenic), leucine solely to fats (ketogenic) and isoleucine being both a glucogenic and a ketogenic amino acid. Isoleucine is catabolized via with alpha-ketoglutarate where upon it is oxidized and split into propionyl-CoA and acetyl-CoA. Propionyl-CoA is converted into succinyl-CoA, a TCA cycle intermediate which can be converted into oxaloacetate for gluconeogenesis (hence glucogenic). The acetyl-CoA can be fed into the TCA cycle by condensing with oxaloacetate to form citrate or used in the synthesis of ketone bodies or fatty acids. The different metabolism of BCAAs accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine are required respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. BCAAs are decreased in patients with liver disease, such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia. An inability to break down isoleucine, along with other amino acids, is associated with maple syrup urine disease (MSUD) (PMID: 34125801). Isoleucine, like other BCAAs, is associated with insulin resistance. In particular, higher levels of isoleucine are observed in the blood of diabetic mice, rats, and humans (PMID 25287287). Mice fed an isoleucine deprivation diet for one day have improved insulin sensitivity, and feeding of an isoleucine deprivation diet for one week significantly decreases blood glucose levels (PMID: 24684822).

L-Norleucine, also known as L-aminohexanoate or caprine, belongs to the class of organic compounds known as l-alpha-amino acids. These are alpha amino acids which have the L-configuration of the alpha-carbon atom. Thus, L-norleucine is considered to be a fatty acid lipid molecule. An unnatural amino acid that is used experimentally to study protein structure and function. L-Norleucine is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. L-Norleucine exists in all eukaryotes, ranging from yeast to humans. Outside of the human body, L-Norleucine has been detected, but not quantified in cow milk. This could make L-norleucine a potential biomarker for the consumption of these foods. It binds reversibly to the kringle domain of plasminogen and blocks the binding of plasminogen to fibrin and its activation to plasmin.

2-Amino-4-methylpentanoic acid

Leucine (Leu) or L-leucine is an alpha-amino acid. These are amino acids in which the amino group is attached to the carbon atom immediately adjacent to the carboxylate group (alpha carbon). Amino acids are organic compounds that contain amino (–NH2) and carboxyl (–COOH) functional groups, along with a side chain (R group) specific to each amino acid. L-leucine is one of 20 proteinogenic amino acids, i.e., the amino acids used in the biosynthesis of proteins. Leucine is found in all organisms ranging from bacteria to plants to animals. It is classified as a non-polar, uncharged (at physiological pH) aliphatic amino acid. Leucine is essential in humans, meaning the body cannot synthesize it, and it must be obtained from the diet. Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes. L-Leucine is a branched chain amino acid (BCAA). The BCAAs consist of leucine, valine and isoleucine (and occasionally threonine). BCAAs are essential amino acids whose carbon structure is marked by a branch point at the beta-carbon position. BCAAs are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. BCAAs have different metabolic routes, with valine going solely to carbohydrates (glucogenic), leucine solely to fats (ketogenic) and isoleucine being both a glucogenic and a ketogenic amino acid. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine respectively. The primary metabolic end products of leucine metabolism are acetyl-CoA and acetoacetate; consequently, it is one of the two exclusively ketogenic amino acids, with lysine being the other. Leucine is the most important ketogenic amino acid in humans. The vast majority of l-leucine metabolism is initially catalyzed by the branched-chain amino acid aminotransferase enzyme, producing alpha-ketoisocaproate (alpha-KIC). alpha-KIC is metabolized by the mitochondrial enzyme branched-chain alpha-ketoacid dehydrogenase, which converts it to isovaleryl-CoA. Isovaleryl-CoA is subsequently metabolized by the enzyme isovaleryl-CoA dehydrogenase and converted to beta-methylcrotonyl-CoA (MC-CoA), which is used in the synthesis of acetyl-CoA and other compounds. During biotin deficiency, HMB can be synthesized from MC-CoA via enoyl-CoA hydratase and an unknown thioesterase enzyme, which convert MC-CoA into HMB-CoA and HMB-CoA into HMB respectively. Leucine has the capacity to directly stimulate myofibrillar muscle protein synthesis (PMID 15051860). This effect of leucine arises results from its role as an activator of the mechanistic target of rapamycin (mTOR) (PMID 23551944) a serine-threonine protein kinase that regulates protein biosynthesis and cell growth. The activation of mTOR by leucine is mediated through Rag GTPases. Leucine, like other BCAAs, is associated with insulin resistance. In particular, higher levels of leucine are observed in the blood of diabetic mice, rats, and humans (PMID 25287287). BCAAs such as leucine have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. Persistently low leucine levels can result in decreased appetite, poor feeding, lethargy, poor growth, weight loss, skin rashes, hair loss, and desquamation. Many types of inborn errors of BCAA metabolism exist and these are marked by various abnormalities. The most common form is maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement. Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAAs and at least one form is correctable by supplementation with 10 mg of biotin daily. - BCAAs are useful because they are metabolized primarily by muscle. Stress states - e.g surgery, trauma, cirrhosis, infections, fever and starvation--require proportionately more BCAAs than other amino acids and probably proportionately more leucine than either valine or isoleucine. BCAAs and other amino acids are frequently fed intravenously (TPN) to malnourished surgical patients and in some cases of severe trauma. BCAAs, particularly leucine, stimulate protein synthesis, increase reutilization of amino acids in many organs and reduce protein breakdown. Furthermore, leucine can be an important source of calories, and is superior as fuel to the ubiquitous intravenous glucose (dextrose). - Leucine also stimulates insulin release, which in turn stimulates protein synthesis and inhibits protein breakdown. These effects are particularly useful in athletic training. Huntington's chorea and anorexic disorders both are characterized by low serum BCAAs. These diseases, as well as forms of Parkinson's, may respond to BCAA therapy.

L-alloisoleucine is a branched chain amino acid and is a stereo-isomer of L-isoleucine. It is a common constituent of human plasma (albeit at low levels). L-alloisoleucine is produced as a byproduct of isoleucine transamination. L-Isoleucine is one of the four common amino acids (the 3 others being threonine, hydroxyproline, and hydroxylysine) that have two asymmetric carbon atoms which produce four structural possibilities for the same chemical composition. L-alloisoleucine differs from L-isoleucine by having having different stereochemistry around its beta carbon. Plasma L-alloisoleucine, which is derived from L-isoleucine in vivo, can be used for the diagnosis of maple syrup urine disease (MSUD), a genetic disorder. Indeed, plasma L-alloisoleucine levels above 5 umol/L is the most specific and most sensitive diagnostic marker for all forms of MSUD (PMID: 10508118). In MSUD the degradation of the essential branched-chain L-amino acids leucine, valine, and isoleucine and their derived 2-oxoacids is impaired because of an inherited deficiency in branched-chain 2-oxoacid dehydrogenase complex (EC 1.2.4.4) activity. The accumulation of branched-chain compounds in blood and other body fluids can exert neurotoxic effects.

Piperidine (Azinane after the Hantzsch Widman nomenclature) is an organic compound with the molecular formula (CH2)5NH. This heterocyclic amine consists of a six-membered ring containing five methylene units and one nitrogen atom. It is a colorless fuming liquid with an odor described as ammoniacal, pepper-like; the name comes from the genus name Piper, which is the Latin word for pepper. Piperidine is found in barley, black pepper (Piper nigrum). Piperidine has been found to be a microbial metabolite. Piperidine is a flavouring agent and it is also widely used as a building block and chemical reagent in the synthesis of organic compounds, including pharmaceuticals. Piperidine is a widely used secondary amine. It is used to convert ketones to enamines. Enamines derived from piperidine can be used in the Stork enamine alkylation reaction. Piperidine is used as a solvent and as a base. The same is true for certain derivatives: N-formylpiperidine is a polar aprotic solvent with better hydrocarbon solubility than other amide solvents, and 2,2,6,6-tetramethylpiperidine is highly sterically hindered base, useful because of its low nucleophilicity and high solubility in organic solvents.

Nicotine is an alkaloid found in the nightshade family of plants (Solanaceae), predominantly in tobacco and in lower quantities in tomato, potato, eggplant (aubergine), and green pepper. Nicotine alkaloids are also found in the leaves of the coca plant. Nicotine constitutes 0.3 to 5% of the tobacco plant by dry weight, with biosynthesis taking place in the root and accumulation in the leaves. It is a potent neurotoxin with particular specificity to insects; therefore nicotine was widely used as an insecticide in the past and nicotine derivatives such as imidacloprid continue to be widely used. It has been noted that the majority of people diagnosed with schizophrenia smoke tobacco. Estimates for the number of schizophrenics that smoke range from 75% to 90%. It was recently argued that the increased level of smoking in schizophrenia may be due to a desire to self-medicate with nicotine. More recent research has found the reverse: it is a risk factor without long-term benefit, used only for its short-term effects. However, research on nicotine as administered through a patch or gum is ongoing. As nicotine enters the body, it is distributed quickly through the bloodstream and can cross the blood-brain barrier. On average, it takes about seven seconds for the substance to reach the brain. The half-life of nicotine in the body is around 2 hours. The amount of nicotine inhaled with tobacco smoke is a fraction of the amount contained in the tobacco leaves (most of the substance is destroyed by the heat). The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. For chewing tobacco, often called dip, snuff, or sinus, which is held in the mouth between the lip and gum, the amount released into the body tends to be much greater than smoked tobacco. The currently available literature indicates that nicotine, on its own, does not promote the development of cancer in healthy tissue and has no mutagenic properties. Its teratogenic properties have not yet been adequately researched, and while the likelihood of birth defects caused by nicotine is believed to be very small or nonexistent, nicotine replacement product manufacturers recommend consultation with a physician before using a nicotine patch or nicotine gum while pregnant or nursing. However, nicotine and the increased acetylcholinic activity it causes have been shown to impede apoptosis, which is one of the methods by which the body destroys unwanted cells (programmed cell death). Since apoptosis helps to remove mutated or damaged cells that may eventually become cancerous, the inhibitory actions of nicotine create a more favourable environment for cancer to develop. Thus, nicotine plays an indirect role in carcinogenesis. It is also important to note that its addictive properties are often the primary motivating factor for tobacco smoking, contributing to the proliferation of cancer. Nicotine is a highly toxic alkaloid. It is the prototypical agonist at nicotinic cholinergic receptors where it dramatically stimulates neurons and ultimately blocks synaptic transmission. Nicotine is also important medically because of its presence in tobacco smoke. Nicotine is a hygroscopic, oily liquid that is miscible with water in its base form. As a nitrogenous base, nicotine forms salts with acids that are usually solid and water soluble. Nicotine easily penetrates the skin. As shown by the physical data, free base nicotine will burn at a temperature below its boiling point, and its vapours will combust at 95 °C in the air despite a low vapour pressure. Because of this, most nicotine is burned when a cigarette is smoked; however, enough is inhaled to provide the desired effects. Nicotine is a stimulant drug that acts as an agonist at nicotinic acetylcholine receptors. These are ionotropic receptors composed of five homomeric or heteromeric subunits. In the brain, nicotine binds to nicotinic acetylcholine receptors on dopaminergic neurons in the cortico-limbic pathways. This causes the channel to open and allow conductance of multiple cations including sodium, calcium, and potassium. This leads to depolarization, which activates voltage-gated calcium channels and allows more calcium to enter the axon terminal. Calcium stimulates vesicle trafficking towards the plasma membrane and the release of dopamine into the synapse. Dopamine binding to its receptors is responsible for the euphoric and addictive properties of nicotine. Nicotine also binds to nicotinic acetylcholine receptors on the chromaffin cells in the adrenal medulla. Binding opens the ion channel allowing an influx of sodium which causes depolarization of the cell and activates voltage-gated calcium channels. Calcium triggers the release of epinephrine from intracellular vesicles into the bloodstream, which causes vasoconstriction, increased blood pressure, increased heart rate, and increased blood sugar. Cotinine is a byproduct of the metabolism of nicotine which remains in the blood for up to 48 hours and can be used as an indicator of a person's exposure to smoke. In high doses, nicotine will cause a blocking of the nicotinic acetylcholine receptor, which is the reason for its toxicity and its effectiveness as an insecticide. In lower concentrations, the substance acts as a stimulant in mammals and is one of the main factors responsible for the dependence-forming and energy-boosting properties of tobacco smoking.

A 2-methylpyrrolidine that has (R)-configuration." []

Phenylephrine is an alpha-adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent (PubChem). Phenylephrine is used as a decongestant, available as an oral medicine or as a nasal spray. Phenylephrine is not the most common over-the-counter (OTC) decongestant (wikipedia).

DL-Acetylcarnitine is an acylcarnitine. More specifically, it is an acetic acid ester of carnitine. Acylcarnitines were first discovered more than 70 year ago (PMID: 13825279). It is believed that there are more than 1000 types of acylcarnitines in the human body. The general role of acylcarnitines is to transport acyl-groups (organic acids and fatty acids) from the cytoplasm into the mitochondria so that they can be broken down to produce energy. This process is known as beta-oxidation. According to a recent review [Dambrova et al. 2021, Physiological Reviews], acylcarnitines (ACs) can be classified into 9 different categories depending on the type and size of their acyl-group: 1) short-chain ACs; 2) medium-chain ACs; 3) long-chain ACs; 4) very long-chain ACs; 5) hydroxy ACs; 6) branched chain ACs; 7) unsaturated ACs; 8) dicarboxylic ACs and 9) miscellaneous ACs. Short-chain ACs have acyl-groups with two to five carbons (C2-C5), medium-chain ACs have acyl-groups with six to thirteen carbons (C6-C13), long-chain ACs have acyl-groups with fourteen to twenty once carbons (C14-C21) and very long-chain ACs have acyl groups with more than 22 carbons. DL-Acetylcarnitine is therefore classified as a long chain AC. As a long-chain acylcarnitine DL-Acetylcarnitine is generally formed through esterification with long-chain fatty acids obtained from the diet. The main function of most long-chain acylcarnitines is to ensure long chain fatty acid transport into the mitochondria (PMID: 22804748). Altered levels of long-chain acylcarnitines can serve as useful markers for inherited disorders of long-chain fatty acid metabolism. In particular DL-Acetylcarnitine is elevated in the blood or plasma of individuals with very long chain acyl-CoA dehydrogenase deficiency (PMID: 9034211), colorectal cancer (PMID: 25105552), short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (PMID: 11489939), paclitaxel induced neuropathy (PMID: 29946863), type 2 diabetes Mellitus (PMID: 28726959; PMID: 25964024, PMID: 28726959, PMID: 19369366, PMID: 24358186), chronic heart failure (PMID: 22622056), ornithine transcarbamylase (PMID: 3346778), pre-diabetes (PMID: 23010998, PMID: 24358186), type 1 diabetes mellitus (PMID: 16789638), methylmalonic acidemia (PMID: 8214594), myeloma (PMID: 30096165), and diastolic heart failure (PMID: 26010610). It is also decreased in the blood or plasma of individuals with 3-methyl-crotonyl-glycinuria (PMID: 25732994), antiviral drug induced neuropathy (PMID: 9030365, PMID: 11364244), Alzheimer Disease (PMID: 27196316), major depressive disorder (PMID: 30061399), carnitine palmitoyltransferase 2 deficiency (PMID: 20543534), Familial Mediterranean Fever (PMID: 29900937), chronic fatigue syndrome (PMID: 9854142), methylmalonic acidemia (PMID: 15164354), hepatocellular carcinoma (PMID: 26976432, PMID: 31662827), and coronary artery disease (PMID: 20173117). DL-Acetylcarnitine is elevated in the urine of individuals with colorectal cancer (25105552), uterine fibroids (32590215), heart failure (8070147), diabetes mellitus (10221661), and hepatocellular carcinoma (24923488). It is also decreased in the urine of individuals with carnitine palmitoyltransferase 2 deficiency (20543534). Carnitine palmitoyltransferase I (CPT I, EC:2.3.1.21) is involved in the synthesis of long-chain acylcarnitines (more than C12) on the mitochondrial outer membrane. Elevated serum/plasma levels of long-chain acylcarnitines are not only markers for incomplete FA oxidation but also are indicators of altered carbohydrate and lipid metabolism. High serum concentrations of long-chain acylcarnitines in the postprandial or fed state are markers of insulin resistance and arise from insulin's inability to inhibit CPT-1-dependent fatty acid metabolism in muscles and the heart (PMID: 19073774). Increased intracellular content of long-chain acylcarnitines is thought to serve as a feedback inhibition mechanism of insulin action (PMID: 23258903). In healthy subjects, increased concentrations of insulin effectively inhibits long-chain acylcarnitine production. Several studies have also found increased levels of circulating long-chain acylcarnitines in chronic heart failure patients (PMID: 26796394). The study of acylcarnitines is an active area of research and it is likely that many novel acylcarnitines will be discovered in the coming years. It is also likely that many novel roles in health and disease will be uncovered. An excellent review of the current state of knowledge for acylcarnitines is available at [Dambrova et al. 2021, Physiological Reviews].

p-Octopamine is an amine in traces quantities in plasma and cerebrospinal fluid in humans with septic encephalopathy (PMID 15932098).

A 2-methylpyrrolidine that has (R)-configuration." []

1-Methylpyrrolidine is a natural product found in Arisarum vulgare and Solanum lycopersicum with data available.

Dopamine is a member of the catecholamine family of neurotransmitters in the brain and is a precursor to epinephrine (adrenaline) and norepinephrine (noradrenaline). Dopamine is synthesized in the body (mainly by nervous tissue and adrenal glands) first by the hydration of the amino acid tyrosine to DOPA by tyrosine hydroxylase and then by the decarboxylation of DOPA by aromatic-L-amino-acid decarboxylase. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (dopamine receptors) mediates its action, which plays a major role in reward-motivated behaviour. Dopamine has many other functions outside the brain. In blood vessels, dopamine inhibits norepinephrine release and acts as a vasodilator (at normal concentrations); in the kidneys, it increases sodium excretion and urine output; in the pancreas, it reduces insulin production; in the digestive system, it reduces gastrointestinal motility and protects intestinal mucosa; and in the immune system, it reduces the activity of lymphocytes. Parkinson's disease, a degenerative condition causing tremor and motor impairment, is caused by a loss of dopamine-secreting neurons in an area of the midbrain called the substantia nigra. There is evidence that schizophrenia involves altered levels of dopamine activity, and most antipsychotic drugs used to treat this are dopamine antagonists, which reduce dopamine activity. Attention deficit hyperactivity disorder, bipolar disorder, and addiction are also characterized by defects in dopamine production or metabolism. It has been suggested that animals derived their dopamine-synthesizing machinery from bacteria via horizontal gene transfer that may have occurred relatively late in evolutionary time. This is perhaps a result of the symbiotic incorporation of bacteria into eukaryotic cells that gave rise to mitochondria. Dopamine is elevated in the urine of people who consume bananas. When present in sufficiently high levels, dopamine can be a neurotoxin and a metabotoxin. A neurotoxin is a compound that disrupts or attacks neural tissue. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of dopamine are associated with neuroblastoma, Costello syndrome, leukemia, phaeochromocytoma, aromatic L-amino acid decarboxylase deficiency, and Menkes disease (MNK). High levels of dopamine can lead to hyperactivity, insomnia, agitation and anxiety, depression, delusions, excessive salivation, nausea, and digestive problems. A study has shown that urinary dopamine is produced by Bacillus and Serratia (PMID: 24621061)

Proline betaine is an osmoprotective compound found in urine. It is thought to serve an osmoprotective role for the kidney. Proline betaine is a glycine betaine analogue found in many citrus foods. Elevated levels of proline betaine in human urine are found after the consumption of citrus fruits and juices (PMID: 18060588). Proline betaine is a biomarker for the consumption of citrus fruits.

D-synephrine, also known as (-)-Oxedrine or (-)-Sympatol, is classified as a member of the 1-hydroxy-2-unsubstituted benzenoids. 1-hydroxy-2-unsubstituted benzenoids are phenols that a unsubstituted at the 2-position. D-synephrine is considered to be soluble (in water) and acidic

Beta-leucine is a metabolite that is in the middle of a controversy over its presence in the human body. While there are reports that claim it as a human metabolite, there are others that deny its existence. Two examples:. Circulating levels of beta-leucine are elevated in the cobalamin-deficient state of pernicious anemia. Levels of leucine, on the other hand, are much lower. It is proposed that leucine 2,3-aminomutase, the cobalamin-dependent enzyme that catalyzes the interconversion of leucine and beta-leucine, is the affected enzyme in pernicious anemia and causes these results by preventing the synthesis of leucine from beta-leucine. The synthesis of leucine by human leukocytes and hair roots and by rat liver extracts has been shown to occur when either branched chain fatty acids or valine metabolites are the substances. The synthesis is dependent upon adenosylcobalamin and is inhibited by intrinsic factor (PMID:7430116). Using forms of beta-leucine and leucine that contain several deuterium atoms in place of several hydrogen atoms as internal standards, techniques have been developed which make it possible to detect and quantitate as little as 0.1 mumol/liter of beta-leucine or leucine in human serum and in incubations containing rat liver supernatant. beta-Leucine was not detectable, i.e. less than 0.1 mumol/liter, in any sera from 50 normal human subjects or in any sera from 50 cobalamin-deficient patients. Experiments in which beta-leucine, leucine, isostearic acid, or isocaproic acid were incubated with rat liver supernatant in the presence or absence of adenosylcobalamin or cobalamin-binding protein failed to demonstrate the formation of leucine or beta-leucine or their interconversion under any of the conditions studied. We conclude that beta-leucine is not present in human blood and that the existence of leucine 2,3-aminomutase in mammalian tissues remains to be established (PMID 3356699). Beta-leucine is found to be associated with cobalamin deficiency, which is an inborn error of metabolism.

4-(dimethylamino)benzaldehyde is a member of the class of benzaldehydes that is benzaldehyde carrying a dimethylamino substituent at position 4. Used as an indicator for detection of indoles and hydrazine. It has a role as a chromogenic compound. It is a member of benzaldehydes, a substituted aniline and a tertiary amino compound.

Cytidine is a nucleoside that is composed of the base cytosine linked to the five-carbon sugar D-ribose. Cytidine is a pyrimidine that besides being incorporated into nucleic acids, can serve as a substrate for the salvage pathway of pyrimidine nucleotide synthesis. It is a precursor of cytidine triphosphate (CTP) needed in the phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthetic pathways. These variations probably reflect the species differences in cytidine deaminase, the enzyme that converts cytidine to uridine in the body. The transport of cytidine into the brain's extracellular fluid, and then into neurons and glia, are essential prerequisites for cytidine to be utilized in the brain. An efficient mechanism mediating the brain uptake of circulating cytidine has not yet been demonstrated. The biosynthesis of PC, the most abundant phosphatide in the brain, via the Kennedy pathway requires phosphocholine and cytidine triphosphate (CTP), a cytidine nucleotide involved in the rate-limiting step. The enzyme that converts CTP to endogenous CDP-choline (CTP:phosphocholine cytidylyltransferase) is unsaturated at physiological brain CTP levels. APOBEC is a family of enzymes that has been discovered with the ability to deaminate cytidines on RNA or DNA. The human apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G protein (APOBEC3G, or hA3G), provides cells with an intracellular antiretroviral activity that is associated with the hypermutation of viral DNA through cytidine deamination. Indeed, hA3G belongs to a family of vertebrate proteins that contains one or two copies of a signature sequence motif unique to cytidine deaminases (CTDAs) (PMID: 16769123, 15780864, 16720547).

An N-alkyl glycine that is glycine in which the amino group is replaced by a diethylnitrilo group." []

Propionic acid (PA) is an organic acid. It exists a clear liquid with a pungent and unpleasant smell somewhat resembling body odor. Propionic acid (PA) is widely used as an antifungal agent in food. It is present naturally at low levels in dairy products and occurs ubiquitously, together with other short-chain fatty acids (SCFA), in the gastro-intestinal tract of humans and other mammals as an end-product of the microbial digestion of carbohydrates. The metabolism of propionic acid begins with its conversion to propionyl coenzyme A, the usual first step in the metabolism of carboxylic acids. Since propionic acid has three carbons, propionyl-CoA cannot directly enter either beta oxidation or the citric acid cycles. In most vertebrates, propionyl-CoA is carboxylated to D-methylmalonyl-CoA, which is isomerised to L-methylmalonyl-CoA. Propionic acid has significant physiological activity in animals. Propionic acid is irritant but produces no acute systemic effects and has no demonstrable genotoxic potential (PMID 1628870). The human skin is host of several species of bacteria known as Propionibacteria, which are named after their ability to produce propionic acid. The most notable one is the Cutibacterium acnes (formerly known as Propionibacterium acnes), which lives mainly in the sebaceous glands of the skin and is one of the principal causes of acne. Propionic aciduria is one of the most frequent organic acidurias, a disease that comprise many various disorders. The outcome of patients born with Propionic aciduria is poor intellectual development patterns, with 60% having an IQ less than 75 and requiring special education. Successful liver and/or renal transplantations, in a few patients, have resulted in better quality of life but have not necessarily prevented neurological and various visceral complications. These results emphasize the need for permanent metabolic follow-up whatever the therapeutic strategy (PMID 15868474). Decreased early mortality, less severe symptoms at diagnosis, and more favorable short-term neurodevelopmental outcome were recorded in patients identified through expanded newborn screening. (PMID 16763906)↵ When propionic acid is infused directly into rodents' brains, it produces hyperactivity, dystonia, social impairment, perseveration and brain changes (e.g., innate neuroinflammation, glutathione depletion) that may be used as a means to model autism in rats. Propionic acid is a metabolite of Bacteroides, Clostridium, Dialister, Megasphaera, Phascolarctobacterium, Propionibacterium, Propionigenum, Salmonella, Selenomonas and Veillonella (https://www.mdpi.com/2311-5637/3/2/21).

The S stereoisomer of 2-aminopropiophenone." []

Venoterpine is found in alcoholic beverages. Venoterpine is an alkaloid from Gentiana lutea (yellow gentian

An organic cation obtained by protonation of the imino group of (R)-2-methylpyrrolidine. It is the major microspecies at pH 7.3" []

Acetyl-L-carnitine

Quinoline is an alkaloid from various plant species including Mentha species. Also present in cocoa, black tea and scotch whiskey. Quinoline is a flavouring ingredient Quinoline is a heterocyclic aromatic organic compound. It has the formula C9H7N and is a colourless hygroscopic liquid with a strong odour. Aged samples, if exposed to light, become yellow and later brown. Quinoline is only slightly soluble in cold water but dissolves readily in hot water and most organic solvents. Quinoline is found in alcoholic beverages. Quinoline is mainly used as a building block to other specialty chemicals. Approximately 4 tonnes are produced annually according to a report published in 2005.[citation needed] Its principal use is as a precursor to 8-hydroxyquinoline, which is a versatile chelating agent and precursor to pesticides. Its 2- and 4-methyl derivatives are precursors to cyanine dyes. Oxidation of quinoline affords quinolinic acid (pyridine-2,3-dicarboxylic acid), a precursor to the herbicide sold under the name "Assert"