Acetic anhydride: an intermediate analogue in the acyl-exchange reaction of citramalate lyase.
1. Reactivation of deacetyl citramalate lyase by acetic anhydride proceeds through an enzyme-anhydride complex prior to actual acetylation. The reaction is inhibited by citramalate which is competitive with acetic anhydride. 2. A corresponding complex is an intermediate in the carboxymethylation of deacetyl enzyme by iodoacetate. However, the inhibition of this reaction by S-citramalate appears to be non-competitive with iodoacetate. 3. The results lead to the conclusion that acetic anhydride can be regarded as a structural analogue of citramalic acetic anhydride, the proposed intermediate in the acyl exchange reaction on citramalate lyase. 4. The formation of 6-citryl thiolester from the 1-thiolester via the cyclic citric anhydride provides a chemicla model for enzymic acyl exchange. 5. The data suggest that anhydrides are of general importance in acyl exchange reactions of thiolesters.
D000085:Acetates / Q000494:pharmacology; D000812:Anhydrides / Q000494:pharmacology; D001665:Binding Sites; D003013:Clostridium / Q000201:enzymology; D007461:Iodoacetates / Q000494:pharmacology; D007700:Kinetics; D007652:Oxo-Acid-Lyases / Q000378:metabolism*; D011485:Protein Binding
D000085:Acetates; D000812:Anhydrides; D007461:Iodoacetates; D007652:Oxo-Acid-Lyases