Difference in mode of inhibition between α-D-xylosyl β-D-fructoside and α-isomaltosyl β-D-fructoside in synthesis of glucan by Streptococcus mutans D-glucosyltransferase

• Published in: Carbohydrate research 1986-03, Vol.147 (1), p.135-144
• Main Authors: NISIZAWA, T, TAKEUCHI, K, IMAI, S, KITAHATA, S, OKADA, S
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Carbohydrates; Disaccharides - pharmacology; Fundamental and applied biological sciences. Psychology; Glucans - biosynthesis; Glucosyltransferases - antagonists & inhibitors; Glucosyltransferases - isolation & purification; Kinetics; Oligosaccharides - analysis; Other biological molecules; Streptococcus mutans - enzymology; Structure-Activity Relationship; Trisaccharides - pharmacology
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/0008-6215(86)85012-1

Both alpha-isomaltosyl beta-D-fructoside and alpha-D-xylosyl beta-D-fructoside show strong inhibition of the synthesis of water-insoluble and water-soluble D-glucans from sucrose by a partially purified preparation of a D-glucosyltransferase (GTase) from Streptococcus mutans 6715; however, the inhibitory modes differ substantially. In the presence of alpha-isomaltosyl beta-D-fructoside, the production of reducing sugars and the consumption of sucrose are remarkably enhanced, compared with a control of sucrose alone. Under these conditions, a large proportion of low-molecular-weight glycan (lmwg) and a series of nonreducing oligosaccharides (both containing D-fructosyl groups or residues) are produced. In contrast, in the presence of alpha-D-xylosyl beta-D-fructoside, the production of reducing sugars and the sucrose consumption are strikingly suppressed, and no lmwg or oligosaccharides are produced. Thus, it may be concluded that alpha-isomaltosyl beta-D-fructoside acts as an alternative acceptor for the D-glucosyl and/or D-glucanosyl transfer reactions of the enzyme, and serves to lessen the formation of insoluble and soluble D-glucan, although it stimulates the transferring activity of the enzyme. On the other hand, alpha-D-xylosyl beta-D-fructoside competitively inhibits the sucrose-splitting activity of the enzyme as an analog to sucrose, and thereby diminishes the synthesis of D-glucan.