Martin_1980_Carlsberg.Res.Commun_45_69

Reaction of carboxypeptidase Y with the chromophoric substrate indoleacryloyl imidazole was found to proceed via an acylenzyme intermediate, indoleacryloyl-carboxypeptidase Y, which exhibited a blue shift in lambdamax with increasing pH. Ag+ ions effectively prevented the acylation of the enzyme, while Hg++ ions were found to retard the deacylation of the acyl enzyme intermediate. Cyanylation of the single thiol function in carboxypeptidase Y could be readily achieved in buffer media (pH 7.0) containing 3.3 M urea. Such modification had little effect on the activity of the enzyme towards its typical peptide and ester substrates, suggesting that the thiol group does not participate directly in the catalytic mechanism.