1. The preparation of the ethyl esters of some N-acetyl-S-alkyl- and N-acetyl-S-aryl-cysteine derivatives is described. 2. Kinetic parameters for the hydrolysis of these esters by chymotrypsin are reported. 3. The results are discussed in terms of the mechanism of action of chymotrypsin and also with reference to the possible application to sequence studies of cysteine-containing proteins.
