Phosphorylation of heart phosphofructokinase by Ca2+/calmodulin protein kinase. |
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Authors: | A M Mahrenholz L Lan T E Mansour |
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Institution: | Department of Pharmacology, Stanford University School of Medicine, California 94305. |
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Abstract: | Phosphofructokinase (PFK) from sheep heart was shown to be phosphorylated by Ca2+/calmodulin protein kinase (CaM-kinase) as well as by cyclic AMP-dependent protein kinase (PKA). HPLC analysis of phosphorylated PFK indicated that phosphorylation by CaM-kinase occurs at least at two sites that are distinct from those recognized by PKA. Phosphorylation by either CaM-kinase of PKA resulted in an increase in sensitivity to ATP inhibition and a small but consistent decrease in Ki for ATP. Phosphorylation by either protein kinase caused a slight increase in the Km of PFK for fructose-6-P. Protein kinase C failed to phosphorylate PFK. Combinations of PKA, CaM-kinase and protein kinase C did not alter the stoichiometry of phosphorylation and did not change the effect on enzyme activity. |
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