Fructose 2,6-bisphosphate biosynthesis

Fig. 8.4 The glycolysis pathway in Saccharo-myces and the biosynthesis of ethanol and glycerol. Compounds DHAP, dihydroxyl-acetone monophosphate Fru6P, D-fructose-6-phosphate Frul,6P2, D-fructose-1,6-bisphosphate GA3P, D-glyceraldehyde-3-phosphate GL3P, sn-glycerol-3-phosphate GLAP2, phosphoglycerate-3-phosphate ...

Fig. 1. The reductive pentose phosphate cycle (RPP). The solid lines indicate reactions of the RPP cycle. The number of lines per arrow indicates the number of times each reaction occurs for one complete turn of the cycle in which three molecules of COj are converted to one molecule of G3P. Each reaction of the cycle occurs at least once. The double dashed lines indicate the principal reactions removing intermediate compounds of the cycle for biosynthesis. Abbreviations RuBP, ribulose 1,5-bis-phosphate PGA, 3-phosphoglycerate DPGA, 1,3-diphosphoglycerate, FBP, fructose 1,6-bisphos-phate F6P, fructose 6-phosphate SBP, sedoheptulose 1,7-bisphosphate S7P, sedoheptulose 7-phosphate Xu5P, xylulose 5-phosphate R5P, ribose 5-phosphate Ru5P, ribulose 5-phosphate TPP, thiamine pyrophosphate. From Ref. 1.

F6P is a phosphorylated form of fructose commonly found in cells. F6P is an intermediate in glycolysis, gluconeogenesis, the pentose phosphate pathway, and the Calvin cycle. F6P is a substrate in biosynthesis of the important allosteric factor regulating glycolysis, fructose-2,6-bisphosphate and is also an important precursor of amino sugars (last enzyme below). 

See also Regulation of Gluconeogenesis, Reciprocal Regulation of Glycogen Biosynthesis and Mobilization, Fructose-2,6-Bisphosphate in Gluconeogenesis Regulation... 

Fructose-2,6-bisphosphate and the Control of Gluconeogenesis (Figure 16.7) Glycogen Biosynthesis... 

Overall, from the kinetic properties of muscle adenylosuccinate synthetase reported here, it would appear that the most important regulatory factor in muscle is the availability of IMP. A positive correlation between IMP concentration and adenylosuccinate production in muscle has already been demonstrated (58). The decrease in phosphocreatine during contraction would also lead to an increase in activity. However, hydrolysis of phosphocreatine will produce a concomitant increase in the concentration of inorganic phosphate, which is as good an inhibitor of adenylosuccinate synthetase as phosphocreatine (28). The changes in GDP and fructose 1,6-bisphosphate would appear to oppose this process. Whether these two metabolites serve to dampen the oscillations of the purine nucleotide cycle in vivo is unclear. It has recently been demonstrated that muscle tissue has a significant capacity for de novo purine biosynthesis 104). This requires that the basic... 

Because glucose has twice as many carbons as pyruvate, you should not be surprised to learn that one of the steps in the biosynthesis of glucose is an aldol addition. An enzyme called aldolase catalyzes an aldol addition between dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. The product is fructose-1,6-bisphosphate, which is subsequently converted to glucose. 

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