title: Inositol 1,4,5-trisphosphate 3-kinase activity in frog skeletal muscle.
abstract: Frog skeletal muscle contains a kinase activity that phosphorylates inositol 1,4,5-trisphosphate to inositol 1,3,4,5-tetrakisphosphate. The inositol 1,4,5-trisphosphate 3-kinase activity was mainly recovered in the soluble fraction, where it presented a marked dependency on free calcium concentration in the physiological range in the presence of endogenous calmodulin. At pCa 5, where the activity was highest, the soluble 3-kinase activity displayed a Km for inositol 1,4,5-trisphosphate of 1.6 microM and a Vmax value of 25.1 pmol mg-1 min-1. The removal rates of inositol 1,4,5-trisphosphate by 3-kinase and 5-phosphatase activities of the total homogenate under physiological ionic conditions were very similar, suggesting that both routes are equally important in metabolizing inositol 1,4,5-trisphosphate in frog skeletal muscle.
authors.affiliation: Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Chile, Santiago.
authors.forename: M A
authors.initials: MA
authors.lastname: Carrasco
authors.forename: S
authors.initials: S
authors.lastname: Figueroa
mesh_terms: D000818:Animals; D001001:Anura / Q000378:metabolism*; D000072181:Inositol Polyphosphate 5-Phosphatases; D018482:Muscle, Skeletal / Q000201:enzymology*; D009994:Osmolar Concentration; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*
chemical_list: D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases