Difference in mode of inhibition between α-d-xylosyl β-d-fructoside and α-isomaltosyl β-d-fructoside in synthesis of glucan by Streptococcus mutansd-glucosyltransferase
✍ Scribed by Tosiki Nisizawa; Kanou Takeuchi; Susumu Imai; Sumio Kitahata; Shigetaka Okada
- Book ID
- 102991121
- Publisher
- Elsevier Science
- Year
- 1986
- Tongue
- English
- Weight
- 851 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
Both cu-isomaltosyl @-D-fructoside and ff-D-XylOSyl #3-n-fructoside show strong inhibition of the synthesis of water-insoluble and water-solubie D-glucans from sucrose by a partially purified preparation of a D-glucosyltransferase (GTase) from Streptococcus mutuns 6715; however, the inhibitory modes differ substantially. In the presence of cu-isomaltosyl @-D-fructoside, the production of reducing sugars and the consumption of sucrose are remarkably enhanced, compared with a control of sucrose alane. Under these conditions, a large proportion of low-molecular-weight giycan (lmwg) and a series of noureducing oligosaccharides (both containing u-fructosyl groups or residues) are produced. In contrast, in the presence of ~J-D-xylosylj3-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 tu-isomaltosyl P-D-fructoside acts as an alternative acceptor for the D-glucosyl andfor D-gluca~osyl 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, cu-D-xylosyl ~"~-fructoside competitively inhibits the sucrose-spIi~ting activity of the enzyme as an analog to sucrose, and thereby diminishes the synthesis of D-glucan. Sucrose 6-glucosyltransferase (GTase: EC 2.4.1.5) of Streptococccus mutans is one of the main, causative factors involved in the occurrence of dental caries as the synthesis of water-insoluble D-glucan from sucrose by the enzyme causes bacterial ~.