Amylopectin Chlamydomonas reinhardtii

Delrue, B., Fontaine, T., Routier, F., Decq. A., Wieruszeski, J.-M., Van Den Koomhuyse, N., Maddelein, M.-L., Fournet, B., and Ball, S. 1992. Waxy Chlamydomonas reinhardtii Monocellular algal mutants defective in amylose synthesis and granule-bound starch synthase activity accumulate a structurally modified amylopectin. J. BacterioL 174,3612-3620. 

Isozymes of plant starch synthases (2, 16-20) and branching enzymes (2, 16, 21-26) have been characterized. Presumably, they play distinct roles in amylopectin and amylose synthesis. Also, plant and Chlamydomonas reinhardtii granule-bound starch synthases (27-33) are responsible for synthesis of amylose. Mutants defective in this enzyme are known as waxy mutants and contain starch granules that have little or no amylose. 

Chlamydomonas reinhardtii monocellular algal mutants defective in amylose biosynthesis and granule-bound starch synthase activity accumulate a structurally modified amylopectin. J. Bac-teriol. 1992 174 3612-3620. 

A mutant of starch synthase II has also been isolated in C. reinhardtiL This mutant, st-3, accumulated only 20-40% of amount of starch present in wild type. The enzyme lacking in the mutant was SSII, one of the two starch synthase isoforms present in C. reinhardtii There was also an apparent increase in the amyiose content as well as a modified form of amylopectin. The changes noted in the mutant amylopectin were, a decrease in the number of intermediate glucose branch chains of 8-50 glucose units and an increase in short-chain glucans (2—7 glucose units). The conclusion made was that this SSII was responsible for synthesis of intermediate size branch chains, a similar conclusion reached as indicated above with the function of SSII and SSIIa in higher plants. The SSII of Chlamydomonas is now referred to as SSIII. ... 

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