Substrate Specificity and Subsite Affinities ofβ-Fructofuranosidase fromBifidobacterium adolescentisG1

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Abstract
The substrate specificity of β-fructofuranosidase from Bifidobacterium adolescentis Gl for fructo-oligosaccharides [1F(1-β-d-fructofuranosyl)n−1 sucrose, GFn, (n = 3–8)] and inulooligosaccharides [1F(1-β-d-fructofuranosyl) n−1 fructose, Fn, (n = 2–7)] were investigated. The Km (mm) and k0 (s−1) values were: GF3, 1.1 and 155; GF4, 1.6 and 154; GF5, 3.2 and 252; GF6, 4.2 and 186; GF7, 7.1 and 260; GF8, 7.0 and 180; F2, 4.9 and 213; F3, 1.5 and 423; F4, 2.4 and 311; F5, 1.9 and 458; F6, 8.7 and 369; F7, 8.1 and 323, respectively. The enzyme preferred oligosaccharides to inulin and sucrose as the substrate. The enzyme hardly catalyzed transfructosylation from GF2. The dependence of rate parameters on the degree of polymerization differed from that of Penicillium trzebinskii exo-inulinase. The subsite affinities in the active site were 0.93, 4.33, 1.15, −0.48, 0.38, −1.07, and −0.04 kcal/mol for subsites 1, 2, 3, 4, 5, 6, and 7, respectively.

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