Effects of Corn Bran Hemicellulose and Cecectomy on Acute Ethanol-induced Fatty Liver in Rats

The substrate specificity of honeybee α-glucosidase II, a monomeric protein, was investigated in detail. The enzyme hydrolyzed phenyl α-glucoside and p-nitrophenyl α-glucoside more rapidly than maltooligosaccharides. Unusual kinetics were observed in hydrolysis of sucrose, turanose, kojibiose, and soluble starch. The s versus v plots showed sigmoidal curves, and so the Lineweaver-Burk plots became concave, indicating positive kinetic cooperativity. The Hill coefficients for sucrose, turanose, kojibiose, and soluble starch were calculated to be 1.46, 1.34, 1.15, and 1.28, respectively. The K_m values for these substrates were calculated as the concentration at one half of the maximum velocity. The ratios of the maximum velocities for maltose, malto-triose, -tetraose, -pentaose, -hexaose, -heptaose, maltodextrin (mM, respectively. The enzyme was also active on α-glucose-1-phosphate. Its maximum activity was 79.9% of that to maltose and the K_m was 50 mM. The substrate specificity of this enzyme was different from that of honeybee α-glucosidase I. The two enzymes were found to be immunologically distinct proteins. Based on the rate parameters for maltooligosaccharides, the subsite affinities (A_i’s) in the active site of the enzyme were evaluated. Subsites 1, 2, and 3 having the positive A_i value (A₁, A₂, and A₃: 0.672, 4.61, and 0.483kcal/mol, respectively) were considered to be effective for binding of substrate to the active site.