Starch ADPglucose

SWEETLOVE, L.J., BURRELL, M.M., AP REES, T., Starch metabolism in tubers of transgenic potato (Solanum tuberosum) with increased ADPglucose pyrophosphorylase, Biochem. J., 1996, 320,493-498. 

III. THE ADPglucose PATHWAY IS THE MAJOR PATHWAY OF STARCH SYNTHESIS in Vivo... 

An alternate pathway for starch synthesis has been proposed, which is based on the finding of a putative ADPGlc translocator in the envelope of both amyloplasts and chloroplasts. Akazawa et al. (1991) proposed that ADPglucose is synthesized in the cytosol by the sucrose synthase (rather than in the plastid by the action of the ADPGlc PPase, as is widely accepted), and is then transported into the plastid where it is converted into starch by the starch synthase. A critique of this hypothesis is presented in the chapter, The Site of Starch Synthesis in Nonphotosynthetic Plant Tissues The Amyloplast, where metabolite transport into the plastids is discussed, but it is worth mentioning here that this pathway does not fulfill the criteria mentioned in the preceding—that is, the experimental evidence does not support this alternative pathway. 

Thus, regulation of ADPGlc PPase, at both the transcriptional level and by allosteric control of the enzyme, modulates the rate of ADPglucose synthesis and starch synthesis. 

Anderson, J. M., Okita, T. W., and Preiss, J. 1990. Enhancing carbon flow into starch the role of ADPglucose pyrophosphorylase. In Molecular and Cellular Biology of the Potato (W. C. Park and M. E. Vayda, eds.), pp. 159-180. C. A. B. International, Wallinford, United Kingdom. 

Li, L., and Preiss, J. 1992. Characterization of ADPglucose pyrophosphorylase from a starch-deficient mutant of Arabidopsis thaliana (L.). Carbohyd. Res. 227, 227-239. 

Neuhaus, H. E and Stitt, M. 1990. Control analysis of photosynthate partitioning Impact of reduced activity of ADPglucose pyrophosphorylase or plastid phosphoglucomutase on the fluxes to starch and sucrose in Arabidopsis. Planta. 182,445-454. 

Ozbun, J. L., Hawker, J. S., Greenberg, E., Lammel, C, Preiss, J., and Lee, E. Y. C. 1973. Starch synthetase, phosporylase, ADPglucose pyrophosphorylase and UDP-glucose pyrophosphorylase in developing maize kernels. Plant PhysioL 51,1-5. 

Sanwal, G. G., Greenberg, E., Hardie, J., Cameron, E., and Preiss, J. 1968. Regulation of starch biosynthesis in plant leaves Activation and inhibition of ADPglucose Pyrophosphorylase. Plant Physiol. 43, 417-427. 

Smith, A. M., Bettey, M., and Bedford, I. D. 1989. Evidence that the rb locus alters the starch content of developing pea embryos through an effect on ADPglucose pyrophosphorylase. Plant Physiol. 89,1279-1284. 

Spilatro, S. R., and Preiss, J. 1987. Regulation of starch synthesis in the bundle sheath and mesophyll of Zea mays L. Intercellular compartmentalization of enzymes of starch metabolism and the properties of the ADPglucose Pyrophosphorylases. Plant Physiol. 83, 621-627. 

Stark, D. M., Timmerman, K. P., Barry, G. F., Preiss, J., and Kishore, G. M. 1992. Role of ADPglucose pyrophosphorylase in regulating starch levels in plant tissues. Science 258, 287-292. 

Weber, H., Heim, U., Borisjuk, L., and Wobus, U. 1995. Cell-type specific, coordinate expression of two ADPglucose pyrophosphorylase genes in relation to starch biosynthesis during seed development in Vicia faba L. Planta 195, 352-361. 

Ball S, Marianne T, Dirick L, Fresnoy M, Delrue B, Decq AA. Chlamydomonas reinhardtii low starch mutant is defective for 3-phosphoglycerate activation and orthophosphate inhibition of ADPglucose pyrophosphorylase. Planta 1991 185 17-26. 

Lin T-P, Caspar T, SomerviUe CR, Preiss J. A starch deficient mutant of Arabidopsis thaliana with low ADPglucose pyrophosphorylase activity lacks one of the two subunits of the enzyme. Plant Physiol. 1988 88 1175-1181. 

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