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Mutants of 4‐Oxalocrotonate Tautomerase Catalyze the Decarboxylation of Oxaloacetate through an Imine Mechanism
Author(s) -
Brik Ashraf,
D'Souza Lawrence J.,
Keinan Ehud,
Grynszpan Flavio,
Dawson Philip E.
Publication year - 2002
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/1439-7633(20020902)3:9<845::aid-cbic845>3.0.co;2-2
Subject(s) - decarboxylation , chemistry , tautomer , imine , citrate synthase , stereochemistry , mutant , enzyme , biochemistry , catalysis , gene
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.