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Thioguanine is only found in individuals that have used or taken this drug. It is an antineoplastic compound which also has antimetabolite action. The drug is used in the therapy of acute leukemia. [PubChem]Thioguanine competes with hypoxanthine and guanine for the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and is itself converted to 6-thioguanilyic acid (TGMP), which reaches high intracellular concentrations at therapeutic doses. TGMP interferes with the synthesis of guanine nucleotides by its inhibition of purine biosynthesis by pseudofeedback inhibition of glutamine-5-phosphoribosylpyrophosphate amidotransferase, the first enzyme unique to the de novo pathway of purine ribonucleotide synthesis. TGMP also inhibits the conversion of inosinic acid (IMP) to xanthylic acid (XMP) by competition for the enzyme IMP dehydrogenase. Thioguanine nucleotides are incorporated into both the DNA and the RNA by phosphodiester linkages, and some studies have shown that incorporation of such false bases contributes to the cytotoxicity of thioguanine. Its tumor inhibitory properties may be due to one or more of its effects on feedback inhibition of de novo purine synthesis; inhibition of purine nucleotide interconversions; or incorporation into the DNA and RNA. The overall result of its action is a sequential blockade of the utilization and synthesis of the purine nucleotides.

Homocysteinesulfinic acid, is involved in many metabolic pathways including trans-sulfuration in cysteine synthesis, re-methylation in methionine synthesis,. trans-methylation of DNA, proteins, and lipids, and biosynthesis of small hormonal and neuronal signaling molecules.

N-Acetyltaurine (also known as NAT) is a highly water-soluble and hygroscopic compound formed by the acetylation of taurine. It is both an endogenous metabolite that is constitutively synthesized in the body and an exogenous metabolite formed by ethanol metabolism. NAT is formed by one or multiple N-acetylation reactions between taurine and ethanol metabolites (primarily acetate). The enzyme responsible for NAT synthesis is called NAT synthase, a cytosolic metalloenzyme located in the kidney and liver that can directly catalyze the esterification reaction between taurine and acetate, without the involvement of ATP and CoA. NAT is a potential biomarker of hyperacetatemia as well as ethanol consumption (PMID: 22228769). NAT is typically found in human urine with normal concentrations of 0.599-1.38 umol/mmol creatinine in alcohol-abstinent subjects. NAT can reach average levels of 8.38 umol/mmol creatinine (range 5.39-10.47 umol/mmol creatinine) in subjects consuming alcohol within 3 to 6 h after the start of drinking. Positive NAT results can be used as an indicator for recent alcohol consumption (PMID: 27520321). NAT is considered a direct alcohol biomarker that specifically represents the oxidative pathway of ethanol metabolism. Other direct alcohol biomarkers such as fatty acid ethyl esters (FAEE), ethyl glucuronide, ethyl sulfate, and phosphatidylethanol reflect the non-oxidative pathway of alcohol metabolism. NAT is also elevated in urine after periods of endurance exercise. NAT was previously found in nature as a major component in the sticky droplet of orb spider web. Due to its high hygroscopicity, N-acetyltaurine appears to ensure the orb spider’s web flexibility.

A dihydroxy monocarboxylic acid anion that is the conjugate base of (2,6-dihydroxyphenyl)acetic acid, arising from deprotonation of the carboxy group." []

A dihydroxy monocarboxylic acid anion that is the conjugate base of (2,6-dihydroxyphenyl)acetic (homogentisic) acid, arising from deprotonation of the carboxy group." []

A dihydroxy monocarboxylic acid anion that is the conjugate base of (3,4-dihydroxyphenyl)acetic acid, arising from deprotonation of the carboxy group." []

A 2-hydroxycarboxylate that is obtained by removal of a proton from the carboxylic acid group of 4-hydroxymandelic acid." []

An amino sulfonic acid that is taurine substituted by an acetyl group at the N atom." []