Soluble starch biosynthesis

Maddelein, M.-L., Bellanger, F., Deirue, B., Libessart, N., D hulst, C., Van den Koomhuyse, N., Fontaine, T Wieruszeski, J.-M., Decq. A., and Ball, S. 1994a. Genetic dissection of starch metabolism in the monocellular alga Chlamydomonas reinhardtii Determination of granule-bound and soluble starch synthases functions in amylopectin biosynthesis. J. Biol. Chem. 269, 25150-25157. 

This conclusion was confirmed by kinetic measurements. Preparations of purified cytosolic and plastidic phosphorylase isozymes from Pisum sativum were adjusted to an approximately equal activity concentration (as determined at saturating levels of soluble starch). Using these isozyme preparations kinetic measurements were performed at varying levels of the polysaccharide fraction. Orthophosphate or glucose 1-phosphate levels were saturating. The initial rates of phosphorolysis (Fig. 2A) or of polysaccharide biosynthesis (Fig. 2B) were determined. 

FIGURE 2A and 2B. Polysaccharide-dependent phosphorolysis (A) or biosynthesis (B) catalyzed by purified cytosolic (I) or plastidic (II) isozymes from Pisum sativum. Rates are given as percent of the values obtained at saturatin concentrations os soluble starch. Quantification of the polysaccharide concentrations as in Fig. 1... 

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