Structural and functional insights into intramolecular fructosyl transfer by inulin fructotransferase.
Inulin fructotransferase (IFTase), a member of glycoside hydrolase family 91, catalyzes depolymerization of beta-2,1-fructans inulin by successively removing the terminal difructosaccharide units as cyclic anhydrides via intramolecular fructosyl transfer. The crystal structures of IFTase and its substrate-bound complex reveal that IFTase is a trimeric enzyme, and each monomer folds into a right-handed parallel beta-helix. Despite variation in the number and conformation of its beta-strands, the IFTase beta-helix has a structure that is largely reminiscent of other beta-helix structures but is unprecedented in that trimerization is a prerequisite for catalytic activity, and the active site is located at the monomer-monomer interface. Results from crystallographic studies and site-directed mutagenesis provide a structural basis for the exolytic-type activity of IFTase and a functional resemblance to inverting-type glycosyltransferases.
Jung
Woo-Suk
WS
Department of Agricultural Biotechnology and Center for Agricultural Biomaterials, College of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Hong
Chang-Ki
CK
Lee
Sujin
S
Kim
Chung-Sei
CS
Kim
Soon-Jong
SJ
Kim
Su-Il
SI
Rhee
Sangkee
S
D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology; D003460:Crystallization; D018360:Crystallography, X-Ray; D017931:DNA Primers / Q000737:chemistry; D019281:Dimerization; D005632:Fructose / Q000737:chemistry*; D006602:Hexosyltransferases / Q000378:metabolism / Q000502:physiology*; D008956:Models, Chemical; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D005632:Fructose; D006602:Hexosyltransferases; C021450:inulin fructotransferase (depolymerizing)