Acetyl-L-alanyl-L-alanyl-L-alanine methyl ester: a new highly specific elastase substrate

Acetyl-L-alanyl-L-alanyl-L-alanine methyl ester is a highly specific esteratic substrate for elastase. It is only slowly hydrolyzed by trypsin and α-chymotrypsin (0.13 and 1.2%, respectively, of the rate of elastase), and can be used in crude preparations and for the study of proelastase activation. At pH 8.0 and 25°, K M = 0.43 mM; k cat = 73 s −1 and is independent of pH between 7.5 and 10.5. Acetyl-L-alanine methyl ester is a poor substrate with K M 153 mM and k cat 6.7 s −1 .