Publication Abstract from PubMed
GA (glucoamylase) hydrolyses starch and polysaccharides to beta-D-glucose. RoGA (Rhizopus oryzae GA) consists of two functional domains, an N-terminal SBD (starch-binding domain) and a C-terminal catalytic domain, which are connected by an O-glycosylated linker. In the present study, the crystal structures of the SBD from RoGA (RoGACBM21) and the complexes with beta-cyclodextrin (SBD-betaCD) and maltoheptaose (SBD-G7) were determined. Two carbohydrate binding sites, I (Trp(47)) and II (Tyr(32)), were resolved and their binding was co-operative. Besides the hydrophobic interaction, two unique polyN loops comprising consecutive asparagine residues also participate in the sugar binding. A conformational change in Tyr(32) was observed between unliganded and liganded SBDs. To elucidate the mechanism of polysaccharide binding, a number of mutants were constructed and characterized by a quantitative binding isotherm and Scatchard analysis. A possible binding path for long-chain polysaccharides in RoGACBM21 was proposed.
Crystal structures of the starch-binding domain from Rhizopus oryzae glucoamylase reveal a polysaccharide-binding path.,Tung JY, Chang MD, Chou WI, Liu YY, Yeh YH, Chang FY, Lin SC, Qiu ZL, Sun YJ Biochem J. 2008 Nov 15;416(1):27-36. PMID:18588504[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
