Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 98 (2), 369-74

Deuterium Isotope Effects on Papain Acylation. Evidence for Lack of General Base Catalysis and for Enzyme--Leaving-Group Interaction

Deuterium Isotope Effects on Papain Acylation. Evidence for Lack of General Base Catalysis and for Enzyme--Leaving-Group Interaction

L Polgár. Eur J Biochem.

Abstract

The experimental data presented in this paper comprise kinetic deuterium isotope effects on acylation of papain with various substrates when conducted in H2O and 2H2O. With alkyl esters of N-acylamino acids there is no or very little isotope effect, whereas with N-acylamino acid amides the ratio kappa H2O/kappa 2H2O is less than 1, i.e. there is an inverse isotope effect. Similarly, alkylation of papain with methyl bromoacetate exhibits no kinetic isotope effect, whereas for the analogous alkylation with bromoacetamide an inverse isotope effect is observed. It is concluded that (a) general base catalysis does not occur in the acylation of papain and (b) kinetic deuterium isotope effects can be affected substantially by interaction between the substrate leaving group and the enzyme, which has not been considered in previous mechanistic investigations.

Similar articles

See all similar articles

Cited by 5 articles

LinkOut - more resources

Feedback