Biosynthesis starch branching enzyme

Enzymes Involved in Starch Biosynthesis. Much of the eady data dealing with starch biosynthesis in plants are derived from the study of various mutants. The shrunken-2 and britde-2 mutants of maize have gready reduced levels of ADPGPP activity owing to the absence of one of the two subunits of this enzyme, and result in a shrunken seed appearance. Mendel s eady work on inheritance of traits was performed with a pea mutant deficient in branching enzyme activity (61). Mutations in plants affecting starch biosynthesis can have severe results to plant morphology and viability. 

In nature a cascade of enzyme-catalyzed reactions is involved for the biosynthesis of starch. When selecting the appropriate enzymes and reaction circumstances reactions with multiple enzymes can be performed in vitro. Synthetic glycogen was first synthesized in vitro by Cori [146] in 1943 via the cooperative action of muscle phosphorylase and branching enzymes isolated from rat liver and rabbit heart. 

Interest in the genetic engineering of both plants and micro-organisms for the production of tailor made amylose, amylopectin and/or starches has also been reported. Furthermore, investigations on the enzymatic modification of starch and its major components, for example the introduction of additional branches composed of glucose and/or other monosaccharides and/or uronic acids as well as amino acids or peptides, to produce carbohydrates of possibly comparable functionality to galactomannans, pectin, gum arable, etc., has been initiated. Also studies on the metabolic fate of carbohydrates in food, the biosynthesis of starch, the fine structure of starch from different sources, the effect of electrolytes on the gelatinization of starch and the development of enzymic methods for starch analyses are still active. 

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