title: Tissue distribution, immunoreactivity, and physical properties of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase.
abstract: 6-Phosphofructo-2-kinase (EC 2.7.1.105) and fructose-2,6-bisphosphatase (EC 3.1.3.46) activities were determined in various rat tissues, the latter by using a method based on the formation of a phosphorylated enzyme intermediate during the course of catalysis. Both activities from liver, skeletal muscle, lung, kidney, and testis copurified during polyethylene glycol fractionation, anion-exchange and blue Sepharose chromatography, and gel filtration. The Stokes radius of these enzymes and of the liver bifunctional enzyme was 45 A. Extrahepatic tissues had only 10% or less of the kinase activity found in liver. The results indicate that a liver-type bifunctional enzyme is present in most extrahepatic tissues but that it is minimally expressed. However, the ratio of kinase to bisphosphatase activity in most extrahepatic tissues was 4- to 6-fold higher than in liver, whereas heart 6-phosphofructo-2-kinase had no associated bisphosphatase activity, although its Stokes radius was also 45 A. The heart enzyme was not precipitated by an antiserum to the liver enzyme, whereas only a fraction of the kidney and testis activities was precipitated by this antiserum. The data support the existence of a distinct form of extrahepatic 6-phosphofructo-2-kinase, most readily demonstrated in heart, which may not be bifunctional.
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D003429:Cross Reactions; D007527:Isoenzymes / Q000032:analysis / Q000276:immunology; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D008297:Male; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D010770:Phosphotransferases / Q000032:analysis* / Q000276:immunology / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D013737:Testis / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D010770:Phosphotransferases; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases