EFFECT OF P2' SUBSTITUENTS ON KINETIC CONSTANTS FOR HYDROLYSIS BY CYSTEINE PROTEINASES

Intramolecularly quenched fluorogenic peptide substrates with the general sequence: DABCYL-Lys-Phe-Gly-Gly-Xxx-Ala-EDANS have been utilized to explore the effect of the hydrophobicity of amino acid side chains in the P2′ position on the steady-state kinetic constants for papain catalyzed hydrolysis. The results demonstrate that subsite interactions between the enzyme and the peptide substrate modulate the enzyme specificity by slowing the release of the C-terminal product. This series of substrates can be used to characterize substrate specificity studies of other cysteine proteinases. © 1992.