Molecular cloning and 3D structure prediction of the first raw-starch-degrading glucoamylase without a separate starch-binding domain |
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Authors: | Hostinová Eva Solovicová Adriana Dvorský Radovan Gasperík Juraj |
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Institution: | Department of Biochemistry, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 842 51 Bratislava, Slovakia. umbihost@savba.sk |
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Abstract: | Raw-starch-degrading glucoamylases have been known as multidomain enzymes consisting of a catalytic domain connected to a starch-binding domain (SBD) by an O-glycosylated linker region. A molecular genetics approach has been chosen to find structural differences between two related glucoamylases, raw-starch-degrading Glm and nondegrading Glu, from the yeasts Saccharomycopsis fibuligera IFO 0111 and HUT 7212, respectively. We have found that Glm and Glu show a high primary (77%) and tertiary structure similarity. Glm, although possessing a good ability for raw starch degradation, did not show consensus amino acid residues to any SBD found in glucoamylases or other amylolytic enzymes. Raw starch binding and digestion by Glm must thus depend on the existence of a site(s) lying within the intact protein which lacks a separate SBD. The enzyme represents a structurally new type of raw-starch-degrading glucoamylase. |
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Keywords: | Glucoamylase Saccharomycopsis fibuligera Starch-binding domain Raw starch Primary structure Tertiary structure model |
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