The carboxypeptidase Y-catalysed hydrolysis of aryl trimethylacetates: the nature of the deacylation reaction of trimethylacetylcarboxypeptidase Y

Abstract

The identical k_cat values obtained for the trimethylacetyl esters of 4-nitrophenol, 2,4-dinitrophenol, and 2-chloro-4-nitrophenol support the intermediacy of a trimethylacetyl enzyme in the esterase action of yeast carboxypeptidase Y, the deacylation of which depends on the ionization of an acidic species (pK_app= 5·1) with limiting k_cat values of 0·9 × 10^–2 s^–1 and 2·2 × 10^–2 s^–1 in acidic and basic solutions, respectively.