Structural rearrangements of sucrose phosphorylase from Bifidobacterium adolescentis during sucrose conversion

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The reaction mechanism of sucrose phosphorylase from Bifidobacterium adolescentis (BiSP) was studied by site-directed mutagenesis and x-ray crystallography. An inactive mutant of BiSP (E232Q) was co-crystallized with sucrose. The structure revealed a substrate-binding mode comparable with that seen in other related sucrose-acting enzymes. Wild-type BiSP was also crystallized in the presence of sucrose. In the dimeric structure, a covalent glucosyl intermediate was formed in one molecule of the BiSP dimer, and after hydrolysis of the glucosyl intermediate, a beta-D-glucose product complex was formed in the other molecule. Although the overall structure of the BiSP-glucosyl intermediate complex is similar to that of the BiSP(E232Q)-sucrose complex, the glucose complex discloses major differences in loop conformations. Two loops (residues 336-344 and 132-137) in the proximity of the active site move up to 16 and 4 A, respectively. On the basis of these findings, we have suggested a reaction cycle that takes into account the large movements in the active-site entrance loops.
Original languageEnglish
JournalJournal of Biological Chemistry
Issue number46
Pages (from-to)35576-84
Number of pages9
Publication statusPublished - 2006

    Research areas

  • Bifidobacterium, Binding Sites, Carbohydrate Conformation, Glucosyltransferases, Models, Molecular, Protein Conformation, Sucrose

ID: 40766583