Evaluation of alpha-glucosidase inhibition by using an immobilized assay system.
The inhibitory effects of natural and synthetic inhibitors on the intestinal membrane-bound hydrolase, alpha-glucosidase (AGH), were evaluated by using an immobilized cyanogen bromide-activated Sepharose 4B support. Immobilized AGH (iAGH) inhibition study by synthetic inhibitors (acarbose and voglibose) revealed that the magnitude of inhibition differed from that in the free AGH (fAGH) study: IC50 value of acarbose in iAGH-maltase assay system, 340-430 nM; fAGH, 11 nM. iAGH-maltase inhibition by both inhibitors was influenced by blocking reagents with different functional groups (COOH, OH, CH3, and NH2 groups). On the other hand, significant iAGH-sucrase inhibitory activity was observed only when using the negatively charged support induced by 0.1 M beta-alanine. The Km values obtained in the iAGH assay system were similar to those from the fAGH method. With natural inhibitors, the iAGH-sucrase inhibitory activity of D-Xylose, with in vivo glucose suppression, increased twice compared to that in fAGH. Green tea extract gave almost the same inhibition for both AGH assay systems.
Oki
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T
Division of Bioresource and Bioenvironmental Sciences, Faculty of Agriculture, Graduate School Kyushu University, Fukuoka, Japan.
Matsui
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T
Matsumoto
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K
D000818:Animals; D002384:Catalysis; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D065089:Glycoside Hydrolase Inhibitors; D008320:Maltose / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology; D051381:Rats; D013395:Sucrose / Q000378:metabolism; D013662:Tea
D004791:Enzyme Inhibitors; D065089:Glycoside Hydrolase Inhibitors; D010936:Plant Extracts; D013662:Tea; D013395:Sucrose; D008320:Maltose