Activation of thiamine diphosphate in pyruvate decarboxylase from Zymomonas mobilis
Open Access
- 28 December 1998
- journal article
- research article
- Published by Wiley in FEBS Letters
- Vol. 441 (3) , 404-406
- https://doi.org/10.1016/s0014-5793(98)01594-4
Abstract
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 pK 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.Keywords
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