John F. Robyt

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Three carbohydrate analyses (reducing value by copper-bicinchoninate, total carbohydrate by phenol-sulfuric acid, and D-glucose by glucose oxidase) have been miniaturized using a microsample plate reader. The use of the reducing-value procedure to measure the hydrolysis of starch by alpha-amylase and the use of the glucose oxidase method to measure the(More)
Leuconostoc mesenteroides NRRL B-1355 grows on sucrose to produce two extracellular alpha-D-glucans. Although both are termed dextrans, they are chemically and physically distinct, and can be separated by fractional ethanol precipitation into fractions designated L and S. Fraction L is similar to B-512F dextran, having 95% alpha-(1 goes to 6) linkages and(More)
Reactions of dextransucrase and sucrose in the presence of sugars (acceptors) of low molecular weight have been observed to give a dextran of low molecular weight and a series of oligosaccharides. The acceptor reaction of dextransucrase was examined in the absence and presence of sucrose by using D-[14C]glucose, D-[14C]fructose, and 14C-reducing-end labeled(More)
Leuconostoc mesenteroides B-512 FMC produces dextran and levan using sucrose. Because of the industrial importance of dextrans and oligosaccharides synthesized by dextransucrase (one of glycansucrases from L. mesenteroides), much is known about the dextransucrase, including expression and regulation of gene. However, no detailed report about levansucrase,(More)
Remaud-Simeon and co-workers [Moulis, C.; Joucla, G.; Harrison, D.; Fabre, E.; Potocki-Veronese, G.; Monsan, P.; Remaud-Simeon, M. J. Biol. Chem., 2006, 281, 31254-31267] have recently proposed that a truncated Escherichia coli recombinant B-512F dextransucrase uses sucrose and the hydrolysis product of sucrose, D-glucose, as initiator primers for the(More)
Acarbose analogues, 4IV-maltohexaosyl acarbose (G6-Aca) and 4IV-maltododecaosyl acarbose (G12-Aca), were prepared by the reaction of cyclomaltodextrin glucanyltransferase with cyclomaltohexaose and acarbose. The inhibition kinetics of acarbose and the two acarbose analogues were studied for four different alpha-amylases: Aspergillus oryzae, Bacillus(More)
After chemical mutagenesis using ethyl methane sulfonate, we isolated mutants constitutive for glucansucrases from Leuconostoc mesenteroides NRRL B-512FM, B-1142, and B-1355. Those mutants produced glucansucrases when grown on D-glucose as well as on sucrose. They produced higher glucansucrase activities (3 to 22 times) when grown on D-glucose than the(More)
The production of dextransucrase from Leuconostoc mesenteroides NRRL B-512F was stimulated 2-fold by the addition of 0.005% of calcium chloride to the medium; levansucrase levels were unaffected. Dextransucrase was purified by concentration and dialysis of the culture supernatant with a Bio-Fiber 80 miniplant, and by treatment with dextranase followed by(More)
The acceptor reaction of dextransucrase consists of the transfer of D-glucosyl groups from sucrose to other carbohydrates, and occurs at the expense of dextran synthesis. In the present study, solutions of [14C]sucrose and of each of seventeen acceptor sugars were digested with highly purified Leuconostoc mesenteroides B-512F dextransucrase. The products(More)