Purification and characterization of an oligo-isomaltosaccharide synthase from a Streptococcus sobrinus glucosyltransferase-I deficient mutant.

One glucosyltransferase (GTF) -I deficient mutant of Streptococcus sobrinus strain B13N was isolated through chemical mutagenesis with ethyl methanesu lfonate, and characterized. This mutant, designated as B13N-Id, readily all owed us to purify a homogeneous oligo-isomaltosaccharide synthase (GTF-S) f rom its culture fluid, The purified GTF-S was only recognized with rabbit polyclonal antibody agai nst recombinant GTF-S from an Ecsherichia coli MD124 clone expressing the B 13N gtfS gene, and showed the almost same enzymatic properties as the recom binant enzyme. A double reciprocal plot of the B13N GTF-S for sucrose was b iphasic, and the affinity for this substrate was high compared to that of G TF-S enzymes from other strains,