Streptococcus mutans g 型菌の 1, 3-α-D-glucan synthase による glucan 鎖の合成ならびに伸長に関する研究

抄録

The mechanism for the insolubilization of exogenous 1, 6-α-D-glucan as a primer with 1, 3-α-D-glucan synthase from serotype g Streptococcus mutans was examined. Glucan produced by 1, 3-α-D-glucan synthase was methylated, degraded, and analysed by gas chromatography and quadrupole type gas chromatograph mass spectrometry (GC/MS). The structure of the water-insoluble glucan (IG) produced by 1, 3-α-D-glucan synthase was determined by methylation analysis using GC/MS. It was confirmed qualitatively that four kinds of the partially methylated alditol acetates were derived from the nonreducing terminal residue, 1, 3-α-linked residue, 1, 6-α-linked residue, and branched residue. 1, 3-α-D-glucan synthase was incubated with sucrose and dextran for a given time and only IG was harvested. By repeating the above method using the residual supernatant, five varieties of IG were obtained by changing the reaction time, and their structures were examined. In the glucan insolubilized immediately after initiating the reaction, side chains of 1, 3-α-D-glucan attached closely to 1, 6-α-D-glucan as the main chain. However, the glucan whose side chains were sparsely branched did not insolubilize unless these side chains were extended by further incubation. In other words, the more closely the side chains attached to the main chain, the sooner the glucan insolubilized.