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Activation of thiamine diphosphate in pyruvate decarboxylase from Zymomonas mobilis
Author(s) -
Tittmann Kai,
Mesch Kathrin,
Pohl Martina,
Hübner Gerhard
Publication year - 1998
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(98)01594-4
Subject(s) - zymomonas mobilis , pyruvate decarboxylase , thiamine , chemistry , cofactor , biochemistry , deprotonation , enzyme , pyruvate carboxylase , methionine , glutamine , carboxy lyases , amino acid , ethanol , organic chemistry , ion , ethanol fuel , alcohol dehydrogenase
Replacement of tryptophan 392 located in the active site cavity of pyruvate decarboxylase (PDC; EC 4.1.1.1) from Zymomonas mobilis by methionine or glutamine yields enzymes with smaller catalytic constants of 8.5 s −1 and 3.6 s −1 at 4°C, compared to that of the wild‐type enzyme (17 s −1 ). The rate constants of the H/D exchange at the C2 of the coenzyme thiamine diphosphate have been determined to be 130 s −1 for the wild‐type enzyme, 56 s −1 for the methionine and 30 s −1 for the glutamine mutant, respectively. A group with a p K a of about 5 has been identified to be essential for C2 deprotonation of the enzyme‐bound thiamine diphosphate from the pH dependence of the H/D exchange.