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Deoxyinosine is a nucleoside that is formed when hypoxanthine is attached to a deoxyribose ring (also known as a ribofuranose) via a beta-N9-glycosidic bond. Deoxyinosine is found in DNA while inosine is found in RNA. Inosine is a nucleic acid important for RNA editing. Adenosine deaminase (ADA) catalyzes the conversion of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. ADA-deficient individuals suffer from severe combined immunodeficiency (SCID) and are unable to produce significant numbers of mature T or B lymphocytes. This occurs as a consequence of the accumulation of ADA substrates or their metabolites. Inosine is also an intermediate in a chain of purine nucleotides reactions required for muscle movements. Moreover, deoxyinosine is found to be associated with purine nucleoside phosphorylase (PNP) deficiency, which is an inborn error of metabolism.

Deoxyguanosine, also known as dG, belongs to the class of organic compounds known as purine 2'-deoxyribonucleosides. Purine 2'-deoxyribonucleosides are compounds consisting of a purine linked to a ribose which lacks a hydroxyl group at position 2’. Deoxyguanosine is a nucleoside consisting of the base guanine and the sugar deoxyribose. Deoxyguanosine is one of the four deoxyribonucleosides that make up DNA. Deoxyguanosine exists in all living species, ranging from bacteria to plants to humans. Deoxyguanosine participates in a number of enzymatic reactions. In particular, deoxyguanosine can be biosynthesized from 2'-deoxyguanosine 5'-monophosphate through the enzyme known as cytosolic purine 5'-nucleotidase. In addition, deoxyguanosine can be converted into 2'-deoxyguanosine 5'-monophosphate (dGMP); which is mediated by the enzyme deoxyguanosine kinase. Deoxyguanosine is involved in the rare, inherited metabolic disorder called the purine nucleoside phosphorylase deficiency (PNP deficiency). In particular PNP deficiency is characterized by elevated levels of dGTP (deoxyguanosine triphosphate). PNP accounts for approximately 4% of patients with severe combined immunodeficiency (PMID: 1931007). PNP-deficient patients suffer from recurrent infections, usually beginning in the first year of life. Two thirds of patients have evidence of neurologic disorders with spasticity, developmental delay and mental retardation. Deoxyguanosine can be converted to 8-hydroxy-deoxyguanosine (8-OHdG) due to hydroxyl radical attack at the C8 of guanine. 8-hydroxy-deoxyguanosine is a sensitive marker of the DNA damage This damage, if left unrepaired, has been proposed to contribute to mutagenicity and cancer promotion.

A 5'-deoxyribonucleoside in which hypoxanthine is attached to 5-deoxyribofuranose via a beta-N(9)-glycosidic bond." []

A 5'-deoxyribonucleoside in which hypoxanthine is attached to 5-deoxyribofuranose via a beta-N(9)-glycosidic bond." []

N-Acetyl-L-methionine or N-Acetylmethionine, belongs to the class of organic compounds known as N-acyl-alpha amino acids. N-acyl-alpha amino acids are compounds containing an alpha amino acid which bears an acyl group at its terminal nitrogen atom. N-Acetylmethionine can also be classified as an alpha amino acid or a derivatized alpha amino acid. Technically, N-Acetylmethionine is a biologically available N-terminal capped form of the proteinogenic alpha amino acid L-methionine. N-acetyl amino acids can be produced either via direct synthesis of specific N-acetyltransferases or via the proteolytic degradation of N-acetylated proteins by specific hydrolases. N-terminal acetylation of proteins is a widespread and highly conserved process in eukaryotes that is involved in protection and stability of proteins (PMID: 16465618). About 85% of all human proteins and 68% of all yeast proteins are acetylated at their N-terminus (PMID: 21750686). Several proteins from prokaryotes and archaea are also modified by N-terminal acetylation. The majority of eukaryotic N-terminal-acetylation reactions occur through N-acetyltransferase enzymes or NAT’s (PMID: 30054468). These enzymes consist of three main oligomeric complexes NatA, NatB, and NatC, which are composed of at least a unique catalytic subunit and one unique ribosomal anchor. The substrate specificities of different NAT enzymes are mainly determined by the identities of the first two N-terminal residues of the target protein. The human NatA complex co-translationally acetylates N-termini that bear a small amino acid (A, S, T, C, and occasionally V and G) (PMID: 30054468). NatA also exists in a monomeric state and can post-translationally acetylate acidic N-termini residues (D-, E-). NatB and NatC acetylate N-terminal methionine with further specificity determined by the identity of the second amino acid. N-acetylated amino acids, such as N-acetylmethionine can be released by an N-acylpeptide hydrolase from peptides generated by proteolytic degradation (PMID: 16465618). In addition to the NAT enzymes and protein-based acetylation, N-acetylation of free methionine can also occur. In particular, N-Acetylmethionine can be biosynthesized from L-methionine and acetyl-CoA by the enzyme methionine N-acetyltransferase (EC 2.3.1.66). Excessive amounts N-acetyl amino acids including N-acetylmethionine (as well as N-acetylglycine, N-acetylserine, N-acetylglutamine, N-acetylglutamate, N-acetylalanine, N-acetylleucine and smaller amounts of N-acetylthreonine, N-acetylisoleucine, and N-acetylvaline) can be detected in the urine with individuals with acylase I deficiency, a genetic disorder (PMID: 16465618). Aminoacylase I is a soluble homodimeric zinc binding enzyme that catalyzes the formation of free aliphatic amino acids from N-acetylated precursors. In humans, Aminoacylase I is encoded by the aminoacylase 1 gene (ACY1) on chromosome 3p21 that consists of 15 exons (OMIM 609924). Individuals with aminoacylase I deficiency will experience convulsions, hearing loss and difficulty feeding (PMID: 16465618). ACY1 can also catalyze the reverse reaction, the synthesis of acetylated amino acids. Many N-acetylamino acids, including N-acetylmethionine are classified as uremic toxins if present in high abundance in the serum or plasma (PMID: 26317986; PMID: 20613759). Uremic toxins are a diverse group of endogenously produced molecules that, if not properly cleared or eliminated by the kidneys, can cause kidney damage, cardiovascular disease and neurological deficits (PMID: 18287557).

Indole is an aromatic heterocyclic organic compound. It has a bicyclic structure, consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring. The participation of the nitrogen lone electron pair in the aromatic ring means that indole is not a base, and it does not behave like a simple amine. Indole is a microbial metabolite and it can be produced by bacteria as a degradation product of the amino acid tryptophan. It occurs naturally in human feces and has an intense fecal smell. At very low concentrations, however, indole has a flowery smell and is a constituent of many flower scents (such as orange blossoms) and perfumes. As a volatile organic compound, indole has been identified as a fecal biomarker of Clostridium difficile infection (PMID: 30986230). Natural jasmine oil, used in the perfume industry, contains around 2.5% of indole. Indole also occurs in coal tar. Indole has been found to be produced in a number of bacterial genera including Alcaligenes, Aspergillus, Escherichia, and Pseudomonas (PMID: 23194589, 2310183, 9680309). Indole plays a role in bacterial biofilm formation, bacterial motility, bacterial virulence, plasmid stability, and antibiotic resistance. It also functions as an intercellular signalling molecule (PMID: 26115989). Recently, it was determined that the bacterial membrane-bound histidine sensor kinase (HK) known as CpxA acts as a bacterial indole sensor to facilitate signalling (PMID: 31164470). It has been found that decreased indole concentrations in the gut promote bacterial pathogenesis, while increased levels of indole in the gut decrease bacterial virulence gene expression (PMID: 31164470). As a result, enteric pathogens sense a gradient of indole concentrations in the gut to migrate to different niches and successfully establish an infection.

3'-deoxyinosine is a purine 3'-deoxyribonucleoside that is inosine in which the hydroxy group at position 3' is replaced by a hydrogen.

A racemate comprising equimolar amounts of N-acetyl-L-methionine and N-acetyl-D-methionine." []

Aesculetin, also known as cichorigenin or cichoriin aglucon, belongs to the class of organic compounds known as 6,7-dihydroxycoumarins. These are coumarins bearing two hydroxyl groups at positions 6 and 7 of the coumarin skeleton, respectively. Aesculetin is found, on average, in the highest concentration within sherries. Aesculetin has also been detected, but not quantified, in several different foods, such as horseradish, carrots, dandelions, grape wines, and highbush blueberries. This could make aesculetin a potential biomarker for the consumption of these foods.

2-aminonaphthalene belongs to the family of Naphthalenes. These are compounds containing a naphthalene moiety, which consists of two fused benzene rings.

A 3'-deoxyribonucleoside having guanine as the nucleobase." []

Anabasine is a pyridine and piperidine alkaloid found in the Tree Tobacco (Nicotiana glauca) plant, a close relative of the common tobacco plant (Nicotiana tabacum). It is a structural isomer of, and chemically similar to, nicotine. Its principal (historical) industrial use is as an insecticide. Anabasine is a nicotinic receptor agonist toxin and Cholinesterase inhibitor which acts upon the nicotinic acetylcholine receptors. Anabasine is an unstable yellow liquid which is succeptable to light, heat and moisture. It's decomposition products include Nitrogen oxides, carbon monoxide, irritating and toxic fumes and gases and carbon dioxide.

2'-O-Methyladenosine is a methylated adenine residue. 2'-O-Methyladenosine is a naturally occurring 2'-O-methylpurine nucleoside with long lasting hypotensive properties; resistance of 2'-O-methyladenosine against adenosine deaminase is thought to contribute to prolonged activity. 2'-O-Methyladenosine occurs in human fluids, and they increase in urines of untreated adenosine deaminase (ADA) deficient patients (OMIM 608958). (PMID: 9539952, 6980397).

A naphthylamine that is naphthalene substituted by an amino group at position 1." []

7,8-dihydroxycoumarin is a hydroxycoumarin. Daphnetin is a natural product found in Sinacalia tangutica, Solanum tuberosum, and other organisms with data available.

Ginnalin B is a natural product found in Acer pycnanthum and Acer rubrum with data available.

This compound was observed experimentally in |FRAME: TAX-853| (unpublished data, X. Feng, University Medical Center Groningen).

2H-isoindole is an isoindole and a polycyclic heteroarene. It is a tautomer of a 1H-isoindole. Benzopyrroles with the nitrogen at the number two carbon, in contrast to INDOLES which have the nitrogen adjacent to the six-membered ring.

6-Methylquinoline is found in tea. 6-Methylquinoline is a flavouring ingredient.

Quinaldine or 2-methylquinoline is a simple derivative of a heterocyclic compound quinoline.

Nothofagin

Hydroquinone, also known as benzene-1,4-diol, is an aromatic organic compound which is a type of phenol, having the chemical formula C6H4(OH)2. Its chemical structure has two hydroxyl groups bonded to a benzene ring in a para position. Hydroquinone is commonly used as a biomarker for benzene exposure. The presence of hydroquinone in normal individuals stems mainly from direct dietary ingestion, catabolism of tyrosine and other substrates by gut bacteria, ingestion of arbutin-containing foods, cigarette smoking, and the use of some over-the-counter medicines. Hydroquinone is a white granular solid at room temperature and pressure. The hydroxyl groups of hydroquinone are quite weakly acidic. Hydroquinone can lose an H+ from one of the hydroxyls to form a monophenolate ion or lose an H+ from both to form a diphenolate ion. Hydroquinone has a variety of uses principally associated with its action as a reducing agent which is soluble in water. It is a major component of most photographic developers where, with the compound Metol, it reduces silver halides to elemental silver.

A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by an azido group. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA during reverse transcription. It improves immunologic function, partially reverses the HIV-induced neurological dysfunction, and improves certain other clinical abnormalities associated with AIDS. Its principal toxic effect is dose-dependent suppression of bone marrow, resulting in anemia and leukopenia. [PubChem]