Substrate specificity of .ALPHA.-glucosidase II in rice seed.
Open Access
- 1 January 1979
- journal article
- Published by Oxford University Press (OUP) in Agricultural and Biological Chemistry
- Vol. 43 (10) , 2131-2135
- https://doi.org/10.1271/bbb1961.43.2131
Abstract
The substrate specificity of rice α-glucosidase 11 was studied. The enzyme was active especially on nigerose, phenyl-a-maltoside and maltooligosaccharides. The actions on isomal-tose and phenyl-α-glucoside were weak, and on sucrose and methyl-α-glucoside, negligible. The α-glucans, such as soluble starch, amylopectin, β-limit dextrin, glycogen and amylose, were also hydrolyzed. The ratio of the maximum velocities for hydrolyses of maltose (G2), nigerose (N), kojibiose (K), isomaltose (I), phenyl-α-maltoside (φM) and soluble starch (SS) was estimated to be 100:94.4:14.2:7.1:89.5:103.1 in this order, and that for hydrolyses of malto-triose (G3), -tetraose (G4), -pentaose (G5), -hexaose (G6), -heptaose (G7), -octaose (G8), and amyloses (G-13 and G-17), 113-.113:113-.106:113:100:106-.106- The Km values for φN, K, I, φM and SS were 2.4mM, 0.58mM, 20mM, 1.6mM and 5.0 mg/ml, respectively; those for G2, G3, G4, G5, G6, G7, G8, G-13 and G-17, 2.4mM, 2.2mM, 2.1mM, 1.5mM, 1.0mM, 1.1mM, 0.95mM, 1.5mM and 1.1mM. Rice α-glucosidase II is considered an enzyme with a preferential activity on maltooligosac-charides.Keywords
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