Biosynthesis of starch

The various soluble starch synthetases extend ot-(l- 4)-glucans, starting from chain lengths of various sizes. SSI, for example, appears to have an extended starch-binding-domain at the C-terminus and transfer glucose residues up to a chain length of about 10. The three other soluble starch synthetases found in cereals (SSIIa, SSIIb and SSIII) appear to make longer chains between clusters there is a possibility that branches may have to be introduced before some of them operate. 

The only naturally occurring covalent modification of starch (apart from the hypothetical link to primer) is phosphorylation. In potato, phosphorylation of 

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Erlander, S. R. (1998a). Starch biosynthesis. I. The size distributions of amylose and amylo-pectin and their relationships to the biosynthesis of starch. Starch/Stdrke. 50,227-240. 

J. Preiss Regulatory mechanisms involved in the biosynthesis of starch... 

Because the reaction is degradative, it requires a starch chain, and the product of a single event is a-Glc 1-P and a starch chain that has had one or more glucosyl residues removed. It is, therefore, not surprising that the reaction in the reverse synthetic direction also requires a starch chain or so-called primer. The primer hypothesis for the synthesis of polysaccharide was, thus, developed from an enzyme that was actually a degradative enzyme and not a synthetic enzyme. Nevertheless, the primer-dependent mechanism has been incorrectly assumed for the biosynthesis of starch for over 60 years. 

Geddes, R., Greenwood, C. T., and Mackenzie, S. 1965. Studies on the biosynthesis of starch granules. Part III. The properties of the components of starches from the growing potato tubers. Carbohyd. Res. 1, 71-82. 

Ghosh, H. P., and Preiss, J. 1966. Adenosine diphosphate glucose pyrophosphorylase A regulatory enzyme in the biosynthesis of starch in spinach chloroplasts. J. Biol. Chem. 241, 4491-4505. 

Kram, A. 1995. Structure and Biosynthesis of Starch The Localization of Starch Synthesizing Enzymes with the Use of Immunoelectron Microscopy. PhD thesis. University of Groningen, The Netherlands. 

Lavintman, N., Tandecarz, J., Carceller, M., Mendiara, S., and Cardini, C. E. 1974. Role of uridine diphosphate glucose in the biosynthesis of starch Mechanism of formation and enlargement of a glucoproteic acceptor. Eur. J. Biochem. 50,145-155. 

Preiss, J. 1982a. Biosynthesis of starch and its regulation. In Encyclopedia of Plant Physiology Plant Carbohydrates (W. Tanner and F. Loewus, eds.), Vol. 13A, pp. 397-417. Springer-Verlag, Berlin, Germany. 

Reibach, P. H., and Benedict, C. R. 1982. Biosynthesis of starch in proplastids of germinating Ricinus communis endosperm tissue. Plant Physiol 70, 252-256. 

This extraordinary structure leads to an understanding of some important mechanisms in the biosynthesis of starch. There is evidence for formation of a so-called "coacervate", in other words a phase separation. The tendency of imits like those shown in Fig. 8.4 to crystallise is obvious - the possibility of close-packing of adjacent units exists, as well as close packing within each imit. A direct consequence of lateral packing of such units is that the enzyme... 

Erlander, S., Biosynthesis of starch, Zywn. Technol. Jakosc, Suppl. 4, 112, 1998. 

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. 

J. Preiss H. P. Ghosh J. Wittkop, Regulation of the Biosynthesis of Starch in Spinach Leaf Chloroplasts In Biochemistry of Chloroplast, T. W. Goodwin, Ed. Academic Press New York, 1967 Vol. 2, pp 131-153. 

J. Preiss, Biosynthesis of Starch and its Regulation In The Biochemistry ofPtants Voi. 14, Carbohydrates, Structure and Functio J. Preiss, Ed. Academic Press New York, 1988 pp 184-249. 

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