Muscle phospho-fructokinase

Hand, S.C., and G.N. Somero (1982). Urea and methylamine effects on rabbit muscle phospho-fructokinase. J. Biol. Chem. 257 734-741. 

A number of other enzymopathic substances (e.g., pyruvate kinase. Chapter 13 and pyrimidine-5 -nucleotidase. Chapter 27), abnormal hemoglobins (Chapter 28), and abnormalities of the erythrocyte cytoskeleton (Chapter 10) may cause hemolytic anemia. Because many enzymes in the red cell are identical to those in other tissues, defects in these enzymes may have pleiotropic effects. Thus, in addition to hemolytic anemia, triose phosphate isomerase deficiency causes severe neuromuscular disease, and phospho-fructokinase deficiency causes a muscle glycogen storage disease (Chapter 13). Mutations that result in decreased enzyme stability are usually most strongly expressed in erythrocytes because of their inability to synthesize proteins. 

Randle has reviewed his concept of a glucose-fatty acid cycle, with some new experimental material. 5 There has been a recent review of gluconeogenesis, with good current references.The control of phospho-fructokinase, one of the important rate limiting enzymes of glycolysis, is still not fully understood. The activity of the enzyme in mammalian muscle is influenced by substrate concentration and by wiiich can acti-... 

Van Schaftingen, E. Hers, H.-G. Purification and properties of phospho-fructokinase 2/fructose 2,6-bisphosphatase from chicken liver and from pigeon muscle. Eur. J. Biochem., 159, 359-365 (1986)... 

Pyruvate kinase is the enzyme that catalyzes this reaction. Like phospho-fructokinase, it is an allosteric enzyme consisting of four suhunits of two different types (M and L), as we saw with phosphofructokinase. Pyruvate kinase is inhibited hy ATP. The conversion of phosphoenolpyruvate to pyruvate slows down when the cell has a high concentration of ATP—that is to say, when the cell does not have a great need for energy in the form of ATP. Because of the different isozymes of pyruvate kinase found in liver versus muscle, the control of glycolysis is handled differently in these two tissues, which we will look at in detail in Chapter 18. 

The fate of fructose-1-phosphate is varied—it may be phosphorylated again in the presence of 1-phospho-fructokinase, magnesium, and ATP to yield fructose-1,6-diphosphate and ADP. 1-Phosphofructokinase is found in liver and muscle. Fructose-1,6-diphosphate may then be used by the glycolytic cycle. 

---