Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus.
Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.
McAlister
D
D
Department of Microbiology and Immunology, University of Louisville, Kentucky 40292.
Doyle
R J
RJ
Taylor
K G
KG
D002236:Carbohydrate Conformation; D004187:Disaccharides / Q000494:pharmacology*; D005936:Glucans / Q000096:biosynthesis* / Q000494:pharmacology*; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D007534:Isomaltose / Q000494:pharmacology*; D008320:Maltose / Q000494:pharmacology*; D008970:Molecular Weight; D013291:Streptococcus / Q000201:enzymology*
D004187:Disaccharides; D005936:Glucans; C014637:laminaribiose; D007534:Isomaltose; D008320:Maltose; D005964:Glucosyltransferases