Unusual solvent isotope effects on the aminoacylase‐catalyzed hydrolysis of acetylamino acids

FEBS Letters

Röhm, Klaus-Heinrich¹  Henseling, Johannes¹ 

[1] Institut für Physiologische Chemie der Philipps-Universität, D-3550 Marburg (Lahn), FRG

关键词: Aminoacylase;    Kinetics;    Reaction mechanism;    Solvent isotope effect;    (Hog kidney);   

DOI  :  10.1016/0014-5793(87)81184-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The deuterium solvent isotope effect on hydrolysis of acetylamino acids catalyzed by porcine kidney aminoacylase I (EC 3.5.1.14) was studied. With Ac-L-Met, a ‘standard’ aminoacylase substrate, the effect was normal at low pH (k _cat(D)/k _cat(H) = 0.7 at pH 6), virtually absent at neutrality, and distinctly inverse (k _cat(D)/K _cat(H) = 1.4) at pH 9. K_m was not significantly affected. The rates of Ac-L-Phe hydrolysis in D₂O considerably exceeded those in H₂O at any pH between 6.5 and 9. We explain this unusual effect of D₂O on aminoacylase I catalysis by an inverse equilibrium effect partially cancelling or, at high pH, reversing a normal isotope effect on k _cat.

【 授权许可】

Unknown