Vol. 118, No. 1, 1984 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS January 13, 1984 Pages 317-323 WPHILE SPECIFICITY IN CHYMOIliYPSIN PEFTIDE SYNTHESIS D.D.Petkov and Iv.Stoineva Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia 1040, Bulgaria Received November 17, 1983 The partitioning of the acylenzyme acetyl-(Gly)n-Phe(N02)-chymotrypsin (n=O, 1,2) to peptide and peptide acid is observed spectrq&otmetrically. Values of partitioning ratios for various nucleuphiles are calculated frcxn the spectral data. They are a measure for the "true" nuclecphile reactivity a@ are useful in the prediction of the best experimental ccrkditicns in enzymic peptide synthesis. A large difference in the nuclecphile reactivity is observed which is attributed to the S'-P' interaction. 2 2 Peptide bonds can be formed by themcdynamically or kinetically controlled enzyme aminolysis of specific acids or esters (1). In both cases, the rate constants ratio kq2/k'+3 for the caqetitive partitioning of the acylenzyrm RCOE (Scheme 1) between the amine canponent NH2R' and water, RCCNHR'+E k+Z/Ks' . kM [R"GH] . RCOE-RCXDR"+ E km2 [NH2R’ 1 I kg; “-jfip I$ [H201 controls the preparative yield. The nuclecphilic ccqetition was kinetically analysed by Seydcux and Yon (2). Although the nuclqhilic reactivity of alcohols am? mines is well studied (3-5f, only Fersht et a1.(6) have reported data abut the partitioning ratios of amino acid derivatives in chymotrypsin catalysis. A km km2/ki3 ratio, however, enables the peptide chemist to predict the best experimental conditions for enzymic peptide synthesis. Moreover, being directly related to the nuclecphile reactivity, its determination provides another approach to the study of enzyme speci- ficity. We nm report data on the partitioning of the acylenzymes acetyl- (Gly)n-Phe(N02)-chymotrypsin (n=0,1,2) to peptide and peptide acid, determined by an express spectrcphotcmetric method. 0006-291X/84 $1.50 Copyright 0 1984 by Academic Press, Inc. 317 All rights of reproduction in any form reserved.