NOVEL ONE-STEP PROCESS FOR ENZYMATIC INCORPORATION OF AMINO-ACIDS INTO PROTEINS - PAPAIN-CATALYZED POLYMERIZATION OF L-METHIONINE ETHYL-ESTER AND ITS REGULATION BY ADDING A PROTEIN SUBSTRATE

To enhance a methionine level of soy protein the plastein reaction was replaced by a simplified one-step process which had been newly developed as described in the preceding paper. It was found that during the process L-methionine ethyl ester (H’ Met· OEt) underwent papain-catalyzed polymerization when the enzymatic incubation was carried out in the absence or inadequacy of soy protein. There was a critical point with regard to the ratio of the concentration of H· Met· OEt·HCl ([M]) and that of the soy protein ([S]). A sufficiently low [M)/[S) prevented H· Met· OEt from forming its polymer, permitting efficient incorporation of methionine into soy protein. A high possibility was suggested that in such a case H· Met· OEt acted as a nucleophile amine to be incorporated in the mode of papain-catalyzed aminolysis of protein. © 1979 Taylor & Francis Group, LLC.