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Abstract: Alteration of the lyophilization conditions significantly enhanced not only the activity of insoluble native subtilisin Carlsberg but also that of solubilized enzyme in benzene. The catalytic activity (k(cat)/K-m) for the transesterification reaction of N-acetyl-L-phenylalanine ethyl ester with l- propanol in benzene was enhanced more than 1000 times by the solubilization (100-fold enhancement) and the adjustment of lyophilization conditions (10-fold enhancement). Subtilisin Carlsberg was modified with polyethylene glycol (PEG-Sub) so that it could be solubilized in organic solvents. The effects of pH of the aqueous enzyme solution, of salts, or of a substrate analog in the aqueous solution before the lyophilization process, on the catalytic activity of native subtilisin and PEG-Sub were investigated. The activities of both the native subtilisin and PEG-Sub depended on the pH. The activities of both PEG-Sub and the native subtilisin were enhanced by the presence of salts. The presence of a substrate analog, N-Ac-L-Phe, also enhanced the activity of the native subtilisin and PEG-Sub. These results demonstrated that the organic solvent-solubilized subtilisin was affected by the lyophilization conditions