SUBSTRATE-SPECIFICITY AND SUBSITE AFFINITIES OF BETA-FRUCTOFURANOSIDASE FROM BIFIDOBACTERIUM-ADOLESCENTIS G1

The substrate specificity of beta-fructofuranosidase from Bifidobacterium adolescentis G1 for fructooligosaccharides [1(F)(1-beta-D-fructofuranosyl)(n-1) sucrose, GF(n), (n = 3-8)] and inulooligosaccharides [1(F)(1-beta-D-fructofuranosyl)(n-1) fructose, F-n, (n = 2-7)] were investigated. The K-m (mM) and k(o) (s(-1)) values were: GF(3), 1.1 and 155; GF(4), 1.6 and 154; GF(5), 3.2 and 252; GF(6), 4.2 and 186; GF(7), 7.1 and 260; GF(8), 7.0 and 180; F-2, 4.9 and 213; F-3, 1.5 and 423; F-4, 2.4 and 311; F-5, 1.9 and 458; F-6, 8.7 and 369; F-7, 8.1 and 323, respectively. The enzyme preferred oligosaccharides to inulin and sucrose as the substrate. The enzyme hardly catalyzed transfructosylation from GF(2). 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.