Abstract The hydrolysis of l-tyrosine ethyl ester by Carlsberg subtilisin, subtilisin BPN', and Novo bacterial proteinase has been examined in mixtures of water with various alcohols. The presence of straight chain alcohols resulted in an apparent inhibition of acid release. It was shown that this inhibition could be accounted for by enzyme-catalyzed transesterification reactions between tyrosine ethyl ester and the various alcohols studied. The subtilisin-catalyzed transesterification reactions are very similar to those catalyzed by chymotrypsin, trypsin, and a Pseudomonas fluorescens cholinesterase.