Biochemistry
-
The primary subsite specificities of human leukocyte elastase, cathepsin G, porcine pancreatic elastase, rat mast cell proteases I and II, bovine chymotrypsin A alpha, and the protease from strain V-8 of Staphylococcus aureus have been mapped with a series of tripeptide thiobenzyl ester substrates of the general formula Boc-Ala-Ala-AA-SBzl, where AA represents one of 13 amino acids. In addition, the effects of a P2 Pro and P4 methoxysuccinyl and succinyl groups were investigated. In an attempt to introduce specificity and/or reactivity into the substrate Boc-Ala-Ala-Leu-SBzl(X), the 4-chloro-, 4-nitro-, and 4-methoxythiobenzyl ester derivatives were studied. ⋯ A very reactive rat mast cell protease substrate, Boc-Ala-Ala-Leu-SBzl(NO2), was also found. The S. aureus V-8 protease was the most specific enzyme tested since it hydrolyzed only Boc-Ala-Ala-Glu-SBzl. Substituents on the thiobenzyl ester moiety of Boc-Ala-Ala-Leu-SBzl resulted in decreased KM values with human leukocyte elastase and rat mast cell protease I when compared to the unsubstituted derivative.(ABSTRACT TRUNCATED AT 250 WORDS)