Mutants of 4-Oxalocrotonate Tautomerase Catalyze the Decarboxylation of Oxaloacetate through an Imine Mechanism
✍ Scribed by Ashraf Brik; Lawrence J. D'Souza; Ehud Keinan; Flavio Grynszpan; Philip E. Dawson
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 431 KB
- Volume
- 3
- Category
- Article
- ISSN
- 1439-4227
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✦ Synopsis
A designed single amino acid substitution can alter the catalytic activity and mechanism of 4-oxalocrotonate tautomerase (4-OT). While the wild-type enzyme catalyzes only the tautomerization of oxalocrotonate, the Pro1Ala mutant (P1A) catalyzes two reactions--the original tautomerization reaction and the decarboxylation of oxaloacetate. Although the N-terminal amine group of P1A is involved in both reactions, our results support a nucleophilic mechanism for the decarboxylase activity, in contrast to the general acid/base mechanism that has been previously established for the tautomerase activity. These findings demonstrate that a single catalytic group in a 4-OT mutant can catalyze two reactions by two different mechanisms.