title: The isolation and characterization of phosphofructokinase from the epithelial cells of rat small intestine.
abstract: 1. Only a single phosphofructokinase isoenzyme is present in the mucosa of rat small intestine. 2. Mucosal phosphofructokinase was purified to yield a homogeneous preparation of specific activity 175 units/mg of protein. 3. The native enzyme is a tetramer, with monomer Mr 84 500 +/- 5000. 4. The native enzyme may be degraded by the action of endogenous proteinases to give two products with the same specific activity as the native enzyme: degradation occurs in the order native enzyme leads to proteolytic product 1 leads to proteolytic product 2. 5. Proteolytic product 1 has a greater mobility in cellulose acetate electrophoresis at pH8 and binds more strongly to DEAE-cellulose than does native enzyme; the converse is true for proteolytic product 2. 6. Proteolytic product 1 is a tetramer with a monomer Mr about 74 300; proteolytic product 2 is also a tetramer. 7. Native enzyme can only be prepared in the presence of proteinase inhibitors; partial purifications based on simple fractionation of crude mucosal extracts in the absence of proteinases inhibitors contain proteolytic product 2 as the main component and proteolytic product 1 together with little native enzyme. 8. Purified native mucosal phosphofructokinase displayed little co-operativity with respect to fructose 6-phosphate at pH 7.0 and was only weakly inhibited by ATP.
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D004586:Electrophoresis; D004848:Epithelium / Q000201:enzymology; D005260:Female; D007413:Intestinal Mucosa / Q000201:enzymology*; D007583:Jejunum / Q000201:enzymology; D010447:Peptide Hydrolases / Q000494:pharmacology; D010732:Phosphofructokinase-1 / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010732:Phosphofructokinase-1; D010447:Peptide Hydrolases