GLYCOGEN-SYNTHESIS PATHWAY IN STREPTOCOCCUS-MUTANS STRAIN NCTC-10449S AND ITS GLYCOGEN SYNTHESIS DEFECTIVE MUTANT-805

The enzymic pathway for synthesis of α-1,4-glucan (glycogen) was studied in Streptococcus mutans strain NCTC 10449S wild type (WT) and its mutant 805, deficient in power of synthesizing glycogen. Adenosine diphosphate (ADP)-glucose pyrophosphorylase (EC 2.7.7.b) and ADP-glucose-glycogen glucosyltransferase (EC 2.4.1.a) were identified in the 37,000 g-soluble cell fraction. During the growth of the WT and the mutant in complex medium with 2 per cent glucose at constant pH (7.0), both ADP-glucose pyrophosphorylase and ADP-glucose-glycogen glucosyltransferase showed maximal specific activity in mid-logarithmic growth phase. In the WT, which accumulated 15 times more glycogen than the mutant, the specific activity of ADP-glucose pyrophosphorylase was 15 times higher and that of ADP-glucose-glycogen glucosyltransferase 1.5 times higher than in the mutant. Glycogen phosphorylase (EC 2.4.1.1) activity was very low. Gel chromatography on agarose A-1.5 m of membrane-concentrated 37,000 g-soluble cell extract from the WT separated the ADP-glucose pyrophosphorylase from the ADP-glucose-glycogen glucosyltransferase. The two enzymes were separated from each other and were eluted as relatively sharp single peaks. © 1979.