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. 

In addition to substrates noted in Table VII, 3 -AMP, 3, 5 -cyclic AMP, dATP, dADP, dAMP, ADPribose, ADPglucose, 5 -adenosine monosulfate, 5 -adenosine acetate, 5 -adenosine propionate, NAD, FAD, CoA, and nucleosidin were deaminated at appreciable rates. Deamination of ATP was inhibited by orthophosphate, pyrophosphate, triphosphate, and Fe3+ with adenosine none of these substances were effective inhibitors. Effects of other divalent cations were not reported. 

The sugar nucleotides UDPglucose and ADPglucose can be synthesized in plants either by a pyrophosphorylase-type reaction (reactions 3a and 3b Espada, 1962) or via a reversal of the sucrose synthase reaction (reaction 4 Cardini et ai, 1955 de Fekete and Cardini, 1964)... 

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. 

ACTIVATOR SPECIFICITIES OF ADPgLUCOSE PYROPHOSPHORYLASES (ADPGlC PPASE) FROM DIFFERENT ORGANISMS"... 

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. 

Ball, K. L., and Preiss, J. 1992. Evidence for an arginine residue at the allosteric sites of spinach leaf ADPglucose pyrophosphorylase. J. Protein Chem. 11, 231-237. 

Ballicora, M. A., Laughlin, M. J., Fu, Y., Okita, T. W., Barry, G. F., and Preiss, J. 1995. ADPglucose from potato tuber Significance of the N-terminal of the small subunit for catalytic properties and heat stability. Plant Physiol. 109, 245-251. 

Brangeon. J.. Reyss, A., and Prioul, J. -L. 1997. In situ detection of ADPglucose pyrophosphory-lase expression during maize endosperm development. Plant Physiol. Biochem. 35, 847-858. 

Denyer, K., Dunlap, F., Thorbj0tornsen, T., Keeling, P., and Smith, A. M. 1996. The major form of ADPglucose pyrophosphorylase in maize endosperm is extra-plastidial. Plant Physiol. 112, 779-785. 

Dickinson, D. B., and Preiss, J. 1969a. ADPglucose pyrophosphorylase from maize endosperm. Arch. Biochem. Biophys. 130,119-128. 

Fox, J., Kawaguchi, K., Greenberg, E., and Preiss, J. 1976. Biosynthesis of bacterial glycogen. Purification and properties of the Escherichia coli B ADPglucose 1,4-a-D-glucan 4-a-glucosyltranferase. Biochem. 15, 849-857. 

Greene, T. W., Chantler, S. E., Kahn, M. L., Barry, G. F., Preiss, J., and Okita, T. W. 1996. Mutagenesis of the potato ADPglucose pyrophosphorylase and characterization of an allosteric mutant defective in 3-phosphoglycerate activation. Proc. Natl. Acad. Sci. 93, 1509-1513. 

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