Acetyl thioglycolic acid

The enzyme is specific for thiol esters of the type of S-acetyl and S-butyryl glutathione. Besides the three thiol esters already discussed, ethyl thiol-acetate, butyl thiolacetate, acetyl thioglycolic acid, acetyl mercapto propionic acid, S-acetyl-2 mercaptoethanol, acetyl thiomalic, acetyl coenzyme A, and butjryl coenzyme A were inactive with the purified enzyme. Crude extracts of liver attacked butyl thiolacetate and acetyl coenzyme A slowly. 

Synonyms/Trade Names Acetyl mercaptan, Mercaptoacetate, Mercaptoacetic acid, 2-Mercaptoacetic acid, 2-Thioglycolic acid, Thiovanic acid ... 

The observations presented here are for the system GSH or GSSG and AcSG, but similar observations have been made with the free and acetylated forms of 2-mercapto ethanol, thioglycolic acid, coenzyme A, and with di-acetylthioethanolamine and with lipoic acid. 

The structure of the 5,6-dihydroxyindole thioether was finally established by a study of the adrenochrome-thioglycollic acid reaction products. This reaction gave three major indolic products the reduction product 5,6-dihydroxy-A -methylindole (44) the thioether (120) or (121) and a small amount of a third unidentified product [238]. It was not possible to isolate the thioether directly but a stable crystalline acetyl derivative was obtained [242]. The structure of this product was established mainly on the basis of n.m.r. spectroscopic evidence. It was shown that, in fact, the thiol residue was attached to the 4-position (i.e. 4-5 -carboxymethylthio-5,6-dihydroxy-7V-methylindole, (123)) in the indole ring system, since the characteristic long-range coupling of ca. 0-8 Hz which occurs between the protons in the... 

The thiol transacetylase that catalyzes this reaction has been partially purified from extracts of E. coli by Hager and Gunsalus (personal communication), and was shown to be relatively specific. We have recently discovered enzymes in extracts of C. kluyveri (47) and in pigeon-liver extracts (48) that catalyze similar acetyl transfers from acetyl-SCoA to 2-mercap-toethanol, thioglycollate, reduced lipoic acid, and hydrogen sulfide however, GSH and cysteine are relatively inert as acetyl acceptors. It remains to be demonstrated if one or more enzymes are involved in these acyl-transfer reactions. The enzyme-catalyzed reactions are to be differentiated from the nonenzymatic reactions in that they occur readily in more dilute solutions and also at neutral to slightly acid pH. 

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