Structural and Functional Insights into Intramolecular Fructosyl Transfer by Inulin Fructotransferase

• Published in: The Journal of biological chemistry Vol. 282; no. 11; pp. 8414 - 8423
• Main Authors: Jung, Woo-Suk, Hong, Chang-Ki, Lee, Sujin, Kim, Chung-Sei, Kim, Soon-Jong, Kim, Su-Il, Rhee, Sangkee
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16-03-2007; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Bacillus - enzymology; Crystallization; Crystallography, X-Ray; Dimerization; DNA Primers - chemistry; Fructose - chemistry; Hexosyltransferases - metabolism; Hexosyltransferases - physiology; Models, Chemical; Molecular Conformation; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Binding; Protein Conformation; Protein Structure, Secondary; Sequence Homology, Amino Acid
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M607143200

Inulin fructotransferase (IFTase), a member of glycoside hydrolase family 91, catalyzes depolymerization of β-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 β-helix. Despite variation in the number and conformation of its β-strands, the IFTase β-helix has a structure that is largely reminiscent of other β-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.