Molecular cloning and 3D structure prediction of the first raw-starch-degrading glucoamylase without a separate starch-binding domain.
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.
Hostinová
Eva
E
Department of Biochemistry, Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 842 51 Bratislava, Slovakia. umbihost@savba.sk
Solovicová
Adriana
A
Dvorský
Radovan
R
Gasperík
Juraj
J
D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012442:Saccharomycopsis / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013213:Starch / Q000378:metabolism*; D040681:Structural Homology, Protein
D005656:Fungal Proteins; D013213:Starch; D005087:Glucan 1,4-alpha-Glucosidase