title: Hydrolysis of aryl beta-maltotriosides by sweet potato beta-amylase and soybean beta-amylase.
abstract: Sweet potato beta-amylase [EC 3.2.1.2, alpha 1,4-D-glucan maltohydrolase]-catalyzed hydrolyses of aryl beta-maltotriosides with substituents, NO2-, Cl-, and Br- at the o-, m-, and p-positions in the phenyl ring were studied at pH 4.8 and 25 degrees C. The hydrolyses of a few of the maltotriosides by soybean beta-amylase [EC 3.2.1.2, alpha-1,4-D-glucan maltohydrolase] were also studied at pH 5.4 and 25 degrees C. It was found that the aryl beta-maltotriosides were preferentially hydrolyzed into maltose and aryl beta-D-glucosides by both beta-amylases. The Michaelis constant Km and the molecular activity ko were determined for the hydrolyses of these maltotriosides and compared with those of maltotriose and maltotetraose. Aryl beta-maltotriosides were more rapidly hydrolyzed than maltotriose by a factor of 30--80, and more slowly hydrolyzed than maltotetraose by a factor of 10--30, depending on the kinds of substituents. The rapid hydrolysis of aryl beta-maltotrioside as compared with maltotriose may be due to the interaction of an aryl group with the subsite of beta-amylase. This is in contrast with glucoamylase [EC 3.2.1.3, alpha-1,4-D-glucan glucohydrolase] of Rhizopus niveus-catalyzed hydrolysis of phenyl beta-maltoside, whose phenyl group does not interact so much with the subsite of the enzyme.
mesh_terms: D000681:Amylases / Q000378:metabolism*; D005087:Glucan 1,4-alpha-Glucosidase / Q000378:metabolism; D006027:Glycosides / Q000378:metabolism; D007700:Kinetics; D008320:Maltose / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D013025:Glycine max; D001614:beta-Amylase / Q000378:metabolism*
chemical_list: D006027:Glycosides; D009844:Oligosaccharides; D008320:Maltose; D000681:Amylases; D001614:beta-Amylase; D005087:Glucan 1,4-alpha-Glucosidase