3- Phosphoglycerate, from

As shown in Scheme 12.87, D-ribulose-5-phosphate can also be derived from D-glucose-6-phosphate, which, as shown in Scheme 11.13, is generated from dihydroxyacetone monophosphate (i.e., an isomer of 3-phosphoglycerate— from the Calvin cycle). 

Each turn of the cycle may be summarized as the formation of 3 pentose molecules from 5 triose molecules. The carboxylation reaction forms 6 phosphoglycerates from the 3 pentoses. The net increase in compounds of this cycle may be balanced by the withdrawal of substances for the synthesis of cell constituents or, for the most part, by storage of hexose as polysaccharides (Chapter V). 

The net result of photosynthesis is reduction of carbon dioxide to form carbohydrates. A key intermediate is phosphoglyceric acid, from which various simple sugars are produced and disproportionated to form other carbohydrates. 

The stmcture was determined to 2.8 A resolution in the laboratory of Tom Steitz, Yale University, (d) The glycolytic enzyme phospho-glycerate mutase, which catalyzes transfer of a phos-phoryl group from carbon 3 to carbon 2 In phosphoglycerate. The structure was determined to 2.S A resolution in the laboratory of Herman Watson, Bristol University, UK. (Adapted from J. Richardson.)... 

Most of the enzymes mediating the reactions of the Calvin cycle also participate in either glycolysis (Chapter 19) or the pentose phosphate pathway (Chapter 23). The aim of the Calvin scheme is to account for hexose formation from 3-phosphoglycerate. In the course of this metabolic sequence, the NADPH and ATP produced in the light reactions are consumed, as indicated earlier in Equation (22.3). 

C-labeled carbon dioxide is administered to a green plant, and shortly thereafter the following compounds are isolated from the plant 3-phosphoglycerate, glucose, erythrose-4-phosphate, sedoheptulose-l,7-bisphosphate, ribose-5-phosphate. In which carbon atoms will radioactivity be found ... 

T21. Tougard, P., Le, T. H., Minard, P Desmadril, M., Yon, J. M., Bizebard, T., Lebras, G and Dumas, C., Structural and functional properties of mutant Arg203Pro from yeast phosphoglycerate kinase, as a model of phosphoglycerate kinase-Uppsaia. Protein Eng. 9, 181-187... 

Precursor synthesis, i.e., conversion of the carbon substrate (CaHbOc) into a central metabolite, such as 3-phosphoglycerate (PGA), from which all cell constituents are thought to be synthesized ... 

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