Open AccessCoenzyme Binding in Yeast Pyruvate Decarboxylase
Author(s) -
Wittorf John H.,
Gubler Clark J.
Publication year - 1971
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1971.tb01575.x
Subject(s) - thiamine pyrophosphate , pyrophosphate , thiamine , isopentenyl pyrophosphate , cofactor , chemistry , pyruvate decarboxylase , transketolase , enzyme , coenzyme a , yeast , biochemistry , stereochemistry , reductase , alcohol dehydrogenase
A kinetic investigation of the behavior of apopyruvate decarboxylase from Saccharomyces carlsbergensis with thiamine pyrophosphate analogues gave the values of 23 μM as the K m for thiamine pyrophosphate and 20 μM as the K m for 2′‐ethylthiamine pyrophosphate. The V for the latter compound was 25%, that of thiamine pyrophosphate. Inhibitor constants, K i , were determined for the following competitive inhibitors of thiamine pyrophosphate with the apoenzyme, (the values are for the pyrophosphate esters): tetrahydrothiamine, 6.5 μM; oxythiamine, 20 μM; 2′‐ n ‐butyIthiamine, 45 μM; 2′‐methoxythiamine, 70 μM; pyrithiamine, 78 μM; 2′‐demethylthiamine, 220 μM; 2′‐hydroxythiamine, 380 μM. None of the inhibitors exhibited coenzyme activity. A hydrophobic interaction of the 2′‐methyl group of thiamine pyrophosphate with the apoenzyme has been proposed and a model for the coenzyme binding site of pyruvate decarboxylase, consisting of a pyrophosphate and a pyrimidine binding region, is discussed.