The Thr45Gly substitution in yeast alcohol dehydrogenase substantially decreases catalysis, alters pH dependencies, and disrupts the proton relay system.

ABSTRACT: X-Ray crystallography shows that the hydroxyl group of Thr-45 in the fermentative alcohol dehydrogenase (ADH1) from Saccharomyces cerevisiae is hydrogen-bonded to the hydroxyl group of the alcohol bound to the catalytic zinc and is part of a proton relay system linked to His-48. The contribution of Thr-45 to catalysis was studied with steady state kinetics of the enzyme with the T45G substitution. Affinities for coenzymes decrease by only 2-4-fold, but the turnover numbers (V/E_t) and catalytic efficiencies (V/K_mE_t) decrease 480-fold and 2900-fold for the oxidation of ethanol and 450-fold and 8400-fold for acetaldehyde reduction, respectively, relative to wild-type enzyme. Binding of NADH appears to require protonation of a group with a pK value of ∼7.4 in w

SUBMITTER: Pal S 

PROVIDER: S-EPMC8530938 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature