Abstract
Lys residues in porcine pancreatic α-amylase (PPA) were N-acylated by N-acyloxysuccinimides (1) and the amylase activity [hydrolytic activity of the α-D- (1, 4) glucoside bond in oligosaccharide] of PPA decreased by about 3515%, while the maltosidase activity (hydrolytic activity of p-nitrophenyl α-D-maltoside) of PPA increased more than 200%. The value of Km for amylase activity showed no change but that of maltosidase activity increased as a result of this chemical modification. The proteinaceous α-amylase inhibitor (phaseolamin) purified from white kidney bean (Phaseolus vulgaris) inhibited both the amylase and maltosidase activity of PPA. With modified PPA, however, amylase activity was inhibited completely but not maltosidase activity. These results indicate the Lys residue in PPA not to be directly related to the amylase activity but involved in some way with maltosidase activity. Furthermore, the incomplete inhibition of modified PPA maltosidase activity indicated the inhibitor not to influence the active site of p-nitrophenyl α-D-maltoside but that of oligosaccharide in modified PPA. The present study demonstrates improved enzyme activity by chemical modification using (1) as a modifier.
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