SPECIFICITY IN THE BINDING OF INHIBITORS TO THE ACTIVE-SITE OF HUMAN PRIMATE ASPARTIC PROTEINASES - ANALYSIS OF P2-P1-P1'-P2' VARIATION

To understand the differences in the binding specificities within the aspartic proteinase family of enzymes, we have carried out studies to determine the inhibition constants of a set of related compounds with various members of the human enzyme family. The inhibition constants ( K(i) values) were determined by competitive inhibition of the hydrolys is of chromogenic octapeptide substrates in the pH range of 3-5. For c omparison, inhibition of monkey renin was studied by RIA at pH 6.0. Al l inhibitors were based on the general structure yl)-L-Phe-P2-(cyclohe xyl)Alapsi[isostere]-P1'-P2'. The isosteric replacements of the scissi le peptide bond included difluorohydroxyethylene, 1,2-diols, 1,3-diols , and difluoroketones. Side chain substituents in P2 include hydrogen, allyl, ethylthio, (methoxycarbonyl)methyl, N-methylthiouridobutyl, im idazolylmethyl, and 4-amino-2-thiazolylmethyl. Our measurements have i dentified potent and selective inhibitors which are useful in evaluati ng the differences in the specificities among selected enzymes of this family.