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Abstract
SUMMARY: Streptococcus mutans strain AHT (serotype g) secretes at least two glucosyltransferases with different pI values. A novel glucosyltransferase with a pI of 5·8 was purified 244-fold from the ammonium sulphate fraction by DEAE-cellulose chromatography, FPLC (Mono Q column, Pharmacia) and hydrophobic chromatography. The enzyme preparation gave a single protein band on analysis by both PAGE and SDS-PAGE, and did not form multiple protein bands detectable by IEF. The M r was estimated to be about 130000 by SDS-PAGE and about 135000 by ultracentrifugal analysis. The apparent K m value and pH optimum of the enzyme were 3·9 ± 0·2 mm (mean ± sd) and about 4·7, respectively. The enzyme synthesized water-soluble glucan from sucrose, and the glucan consisted of over 90 mol% 1,6-α-d-glucosidic linkages. The enzyme activity was not stimulated by primer dextran. Anti-enzyme serum produced a single precipitin band with the purified enzyme preparation, whereas it did not react with either of the other two known glucosyltransferases.
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