title: Phosphorylation of myocardial fructose-6-phosphate,2-kinase: fructose-2,6-bisphosphatase by cAMP-dependent protein kinase and protein kinase C. Activation by phosphorylation and amino acid sequences of the phosphorylation sites.
abstract: Phosphorylation of pure fructose-6-phosphate,2-kinase:fructose-2,6-bisphosphatase from bovine heart by cAMP-dependent protein kinase and protein kinase C was investigated. The major enzyme form (subunit Mr of 58,000) was rapidly phosphorylated by both cAMP-dependent protein kinase and protein kinase C, incorporating 0.8 and 1.0 mol/mol of subunit, respectively. The rate of phosphorylation of the heart enzyme by cAMP-dependent protein kinase was 10 times faster than that of the rat liver enzyme. The minor enzyme (subunit Mr of 54,000), however, was phosphorylated only by protein kinase C and was phosphorylated much more slowly with a phosphate incorporation of less than 0.1 mol/mol of subunit. Phosphorylation by either cAMP-dependent protein kinase or protein kinase C activated the enzyme, but each phosphorylation affected different kinetic parameters. Phosphorylation by cAMP-dependent protein kinase lowered the Km value for fructose 6-phosphate from 87 to 42 microM without affecting the Vmax, whereas the phosphorylation by protein kinase C increased the Vmax value from 55 to 85 milliunits/mg without altering the Km value. The phosphorylated peptides were isolated, and their amino acid sequences were determined. The phosphorylation sites for both cAMP-dependent protein kinase and protein kinase C were located in a single peptide whose sequence was Arg-Arg-Asn-Ser-(P)-Phe-Thr-Pro-Leu-Ser-Ser-Ser-Asn-Thr(P)-Ile-Arg-Arg-Pro. The seryl residue nearest the N terminus was the residue specifically phosphorylated by cAMP-dependent protein kinase, whereas the threonine residue nearest the C terminus was phosphorylated by protein kinase C.
authors.affiliation: Research Service, Veterans Administration Medical Center, Dallas, Texas.
authors.forename: K
authors.initials: K
authors.lastname: Kitamura
authors.forename: K
authors.initials: K
authors.lastname: Kangawa
authors.forename: H
authors.initials: H
authors.lastname: Matsuo
authors.forename: K
authors.initials: K
authors.lastname: Uyeda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004789:Enzyme Activation; D008099:Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D011494:Protein Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D025481:Phosphofructokinase-2; D011493:Protein Kinase C; D010744:Phosphoric Monoester Hydrolases