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- Title
Engineered dextranase from Streptococcus mutans enhances the production of longer isomaltooligosaccharides.
- Authors
Klahan, Patcharapa; Okuyama, Masayuki; Jinnai, Kohei; Ma, Min; Kikuchi, Asako; Kumagai, Yuya; Tagami, Takayoshi; Kimura, Atsuo
- Abstract
Herein, we investigated enzymatic properties and reaction specificities of Streptococcus mutans dextranase, which hydrolyzes α-(1→6)-glucosidic linkages in dextran to produce isomaltooligosaccharides. Reaction specificities of wild-type dextranase and its mutant derivatives were examined using dextran and a series of enzymatically prepared p-nitrophenyl α-isomaltooligosaccharides. In experiments with 4-mg·mL−1 dextran, isomaltooligosaccharides with degrees of polymerization (DP) of 3 and 4 were present at the beginning of the reaction, and glucose and isomaltose were produced by the end of the reaction. Increased concentrations of the substrate dextran (40 mg·mL−1) yielded isomaltooligosaccharides with higher DP, and the mutations T558H, W279A/T563N, and W279F/T563N at the −3 and −4 subsites affected hydrolytic activities of the enzyme, likely reflecting decreases in substrate affinity at the −4 subsite. In particular, T558H increased the proportion of isomaltooligosaccharide with DP of 5 in hydrolysates following reactions with 4-mg·mL−1 dextran.Abbreviations CI: cycloisomaltooligosaccharide; CITase: CI glucanotransferase; CITase-Bc: CITase from Bacillus circulans T-3040; DP: degree of polymerization of glucose unit; GH: glycoside hydrolase family; GTF: glucansucrase; HPAEC-PAD: high performance anion-exchange chromatography-pulsed amperometric detection; IG: isomaltooligosaccharide; IGn: IG with DP of n (n, 2‒5); PNP: p-nitrophenol; PNP-Glc: p-nitrophenyl α-glucoside; PNP-IG: p-nitrophenyl isomaltooligosaccharide; PNP-IGn: PNP-IG with DP of n (n, 2‒6); SmDex: dextranase from Streptococcus mutans; SmDexTM: S. mutans ATCC25175 SmDex bearing Gln100‒Ile732
- Subjects
DEXTRANASE; STREPTOCOCCUS mutans; OLIGOSACCHARIDES
- Publication
Bioscience, Biotechnology & Biochemistry, 2018, Vol 82, Issue 9, p1480
- ISSN
0916-8451
- Publication type
Article
- DOI
10.1080/09168451.2018.1473026