[Nonspecific trypsin substrates in the enzymatic synthesis of peptides]

Trypsin--catalyzed coupling of peptide segments in aqueous medium was studied. Carboxamido methyl esters (Cam esters) of peptides were used as acyl donors. Peptide segments involved in the coupling do not contain positively charged residues (Lys, Arg). Hydrophobic amino acids (except isoleucine and valine) are preferable as C-terminals in the peptide Cam esters used for the reaction. The coupling cannot take place if glutamic or aspartic acids occupy positions 1 or 2 in the amine component. Threefold excess of Cam ester provides a high yield of the coupling product. The coupling is free of secondary hydrolysis. A series of water soluble peptides (from hepta- to tetradecapeptides) were synthesized by this method.