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Crystral Structure of the C-terminal Subunit of Human Maltase-Glucoamylase
Structural highlights
FunctionMGA_HUMAN May serve as an alternate pathway for starch digestion when luminal alpha-amylase activity is reduced because of immaturity or malnutrition. May play a unique role in the digestion of malted dietary oligosaccharides used in food manufacturing. Publication Abstract from PubMedHuman maltase-glucoamylase (MGAM) hydrolyzes linear alpha-1,4-linked oligosaccharide substrates, playing a crucial role in the production of glucose in the human lumen and acting as an efficient drug target for type 2 diabetes and obesity. The amino- and carboxyl-terminal portions of MGAM (MGAM-N and MGAM-C) carry out the same catalytic reaction but have different substrate specificities. In this study, we report crystal structures of MGAM-C alone at a resolution of 3.1 A, and in complex with its inhibitor acarbose at a resolution of 2.9 A. Structural studies, combined with biochemical analysis, revealed that a segment of 21 amino acids in the active site of MGAM-C forms additional sugar subsites (+ 2 and + 3 subsites), accounting for the preference for longer substrates of MAGM-C compared with that of MGAM-N. Moreover, we discovered that a single mutation of Trp1251 to tyrosine in MGAM-C imparts a novel catalytic ability to digest branched alpha-1,6-linked oligosaccharides. These results provide important information for understanding the substrate specificity of alphaglucosidases during the process of terminal starch digestion, and for designing more efficient drugs to control type 2 diabetes or obesity. Structural insight into substrate specificity of human intestinal maltase-glucoamylase.,Ren L, Qin X, Cao X, Wang L, Bai F, Bai G, Shen Y Protein Cell. 2011 Oct;2(10):827-36. Epub 2011 Nov 6. PMID:22058037[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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