Abstract
1. A number of aminoacyl-L-tyrosine ethyl ester hydrochlorides have been synthesized and tested as substrates for α-chymotrypsin.
2. The stability of aminoacyltyrosine esters, in which the aminoacyl substituents are glycyl, L-alanyl, L-α-aminobutyroyl, L-norvalyl, L-norleucyl, L-valyl, L-leucyl, β-alanyl and ε-norleucyl groups, was tested in the absence of the enzyme at pH 8.0.
3. The pH optimum of chymotrypsin activity for glycyltyrosine ethyl ester was found to be near 8.3.
4. The enzyme catalyzes at least two reactions: hydrolysis of the ester linkage to form the corresponding dipeptide and formation of the ninhydrin negative product. β-Alanyl and ε-norleucyl tyrosine esters, however, are simply hydrolyzed, yielding no ninhydrin negative products.
5. The rates of action of the enzyme was decreased markedly by the presence of large side chain groups in the N-terminal L-amino acid residues of the substrates.
