효모 알코올 탈수소효소 아스파르트산-223 잔기의 루신으로 치환과 보조효소의 특이성

Substitution of Asp-223 Residue to Leu in Yeast Alcohol Dehydrogenase and Coenzyme Specificity

Yeast alcohol dehydrogenase (YADH) has an acidic residue that interacts with the 2''- and 3''-hydroxyl groups of the adenosine ribose of the NAD+ coenzyme. The acidic residue of Asp-223 (according to horse liver alcohol dehydrogenase amino acid sequence) is supposed to determine the coenzyme specificity for NAD+ rather than NADP+. We mutated Asp-223 to leucine and the mutant YADH was expressed in yeast and characterized for the coenzyme specificity. The turnover numbers of mutant enzyme for NAD+ and ethanol were decreased 3,5- and 4,8-fold compared to wild-type enzyme, respectively. Contrastively, catalytic specificity for NADP+ was increased 13-fold. As a result, the mutant YADH also employed NADP+ as a coenzyme.