| Autor: |
Døskeland, Anne P., Schworer, Charles M., Døkeland, Stein Ove, Chrisman, Ted D., Soderlin, Thomas R., Corbin, Jackie D., Flatmark, Torgier |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; 11/15/84, Vol. 145 Issue 1, p31-37, 7p |
| Abstrakt: |
1. A calmodulin-dependent protein kinase purified from liver and catalyzed the incorporation of up to 0.7 mol of phosphate per mol subunit phenylalanine 4-monooxygenase. The phosphorylation was accompanied by a proportional increase in the hydroxylase activity. The reaction was Ca2+-dependent and was inhibited by physiological concentrations of phenylalanine. 2. Phenylalanine 4-monooxygenase was also a substrate for the cGMP-dependent protein kinase, but in this system phenylalanine stimulated the rate of phosphorylation to a similar extent as that observed in the reaction catalyzed by cAMP-dependent protein kinase. The hydroxylase was not a substrate for phosphorylase kinase. 3. The calmodulin-dependent reversal of the kinase reaction in the presence of MgADP, was also inhibited by phenylalanine. Since the kinetics of the reverse reaction was the same using 32P-hydroxylase phosphorylated by calmodulin-dependent and cAMP-dependent kinases, it is likely that both kinases phosphorylate the same site on the enzyme. This conclusion was further supported by peptide mapping of tryptic and peptide digests of 32P-hydroxylase, which revealed one major phosphopeptide with enzyme phosphorylated by either kinase. 4. The Ca2+-dependent and calmodulin-dependent phosphorylation described above may mediate the increased phosphorylation of the hydroxylase [Garrison, J. C., Johnsen, D. E., and Campanile, C. P. (1984) J. Biol. Chem. 259, 3283-3292] and its increased activity [Fisher, M. J., Santana, M. A., and Pogson, C. I. (1984) Biochem. J. 219, 87-90] recently observed in hepatocytes exposed to Ca2+-elevating agents. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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