PROTEINASE-CATALYZED PEPTIDE-SYNTHESIS IN CONCENTRATED-SOLUTIONS OF UREA AND OTHER DENATURING AGENTS

Pepsin successfully catalyzed the synthesis of several hydrophobic oct a- and decapeptides in dimethylformamide-water solutions containing co ncentrated urea at pH 4.65. The factors that influence peptide synthes is in the presence of urea were studied using condensation of the trip eptides Z-Ala-Ala-Phe-OH and H-Leu-Ala-Ala-OCH3 as a model. The depend ence of Z-Ala-Ala-Phe-Leu-Ala-Ala-OCH3 yield on pepsin concentration a nd pH, as well as the behavior of pepsin during peptide synthesis were studied. It was shown that pepsin catalyzed the synthesis of Z-Ala-Al a-Phe-Leu-Ala-Ala-OCH3 in guanidine hydrochloride and sodium dodecyl s ulfate solutions. Other proteinases, subtilisin and thermolysin, were applied for the synthesis of p-nitroanilides of tri- and tetrapeptides in urea solutions. Proteinase-catalyzed peptide synthesis in the pres ence of denaturing agents might help to overcome the limitations cause d by poor solubility of the starting peptide derivatives, although thi s effect is sometimes counterbalanced by the product solubility. (C) M unksgaard 1996.