Summary: A water-soluble glucan-synthesizing glucosyltransferase (GTase-S) and a water-insoluble glucan-synthesizing glucosyltransferase (GTase-I) were purified from culture supernatant of 6715 (serotype g) by ammonium sulphate precipitation, chromatofocusing on a Polybuffer exchanger PBE 94 column, and subsequent phenyl-Sepharose CL-4B or hydroxyapatite column chromatography. The GTase-S and GTase-I activities were purified 4019- and 4714-fold, respectively, and the molecular weights were calculated to be 160000 and 165000, respectively. GTase-S had a pH optimum of 5·0, a K of 8·8 mM for sucrose in the presence of 20μM-dextran T10, and an isoelectric point of pH 4·3. GTase-I had two pH optima of 5·0 and 7·0, K values of 4·9 mM (at pH 5·0) and 7·0 mM (at pH 7·0), and an isoelectric point of pH 4·9. Methylation analysis indicated that the water-soluble glucan produced by GTase-S was a highly branched 1,6-α-linked -glucan with 1,3-linked glucose residues, and that the water-insoluble glucan synthesized by GTase-I was composed of 1,3-α-linked glucose units.


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