Starch biosynthesis analysis

Mutations of SSIIa have been observed in wheat and rice.208 In wheat, each of the three wheat genomes were mutated to entirely eliminate expression of the SSIIa gene product, Sgp-1 protein in one line 209 the result was reduced starch amounts and an altered starch structure. In rice, two classes of starch have been found. In Indica rices, the starch is of the long chain variety, while in Japonica, it is of the short chain variety.208 Genetic analysis showed that the mutation in Japonica rice led to a loss of starch synthase II.209 Thus, in higher plants, it seems that loss of SSII activity in dicots and SSIIa activity in monocots have the same results with respect to reduced starch content, due to a lowered amount of amylopectin and altered amylopectin chain size distribution. Thus, these genes may have the same function in starch biosynthesis. 

Besides application to the analysis of polysaccharides of unknown structure, enzymes are also often used for routine measurements on polysaccharides of essentially established structure, such as the starch components and the glycogens. Enzymes provide extremely quick and accurate information for the characterization of polysaccharides of this type, including the products synthesized in vitro diuring studies on their mechanism of biosynthesis. There is also increasing application to the characterization of other types of polysaccharide, synthesized enzymically in vitro. A further important use is for investigation of the nature of the products formed by the action of other catabolic enzymes on polysaccharides such applications may give information on either the structure of the polysaccharide or the specificity of the catabolic enzyme under investigation. 

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