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Regulation of phospholipase D from human hepatocarcinoma cell line by purine nucleotides and protein kinase A

Regulation of phospholipase D from human hepatocarcinoma cell line by purine nucleotides and... The regulation of phosphatidylcholine-specific phospholipase D by purine nucleotides and protein kinase A were studied in vitro using an enzyme preparation partially purified from the membranous fraction of 7721 hepatocarcinoma cells. It was found that the enzyme activity was elevated by low concentrations of some purine nucleotides, but the activating effects were decreased when the concentrations of the nucleotides were higher. The optimal concentrations of GTP, GTPγ[S] , GDP and ATP for maximal activation were 0.1mM, 5μM,1 mM and 1 mM respectively. The activation caused by 1mM ADP was lower. The enzyme was not activated by 1mM AMP, but significant activation was observed by the addition of 1mM cAMP. The latter was mediated by protein kinase A, as a specific inhibitor of protein kinase A ablished the activation. There were synergic effects between ATP and GTP, ATP and PIP2, but not between ATP and GTPγ[S] , or PIP2 and GTPγ[S]. The activating effects of GTP and ATP were abolished by neomycin, a PIP2 scavenger. These results suggest that phospholipase D is regulated by GTP-binding protein and the presence of PIP2 is required for the activation induced by GTP. Protein kinase A may be another protein kinase in addition to protein kinase C and protein tyrosine kinase which regulate the activity of phospholipase D, when the intracellular concentration of cAMP is increased. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Molecular and Cellular Biochemistry Springer Journals

Regulation of phospholipase D from human hepatocarcinoma cell line by purine nucleotides and protein kinase A

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References (22)

Publisher
Springer Journals
Copyright
Copyright © 2000 by Kluwer Academic Publishers
Subject
Life Sciences; Cardiology; Medical Biochemistry; Oncology; Biochemistry, general
ISSN
0300-8177
eISSN
1573-4919
DOI
10.1023/A:1007065408099
Publisher site
See Article on Publisher Site

Abstract

The regulation of phosphatidylcholine-specific phospholipase D by purine nucleotides and protein kinase A were studied in vitro using an enzyme preparation partially purified from the membranous fraction of 7721 hepatocarcinoma cells. It was found that the enzyme activity was elevated by low concentrations of some purine nucleotides, but the activating effects were decreased when the concentrations of the nucleotides were higher. The optimal concentrations of GTP, GTPγ[S] , GDP and ATP for maximal activation were 0.1mM, 5μM,1 mM and 1 mM respectively. The activation caused by 1mM ADP was lower. The enzyme was not activated by 1mM AMP, but significant activation was observed by the addition of 1mM cAMP. The latter was mediated by protein kinase A, as a specific inhibitor of protein kinase A ablished the activation. There were synergic effects between ATP and GTP, ATP and PIP2, but not between ATP and GTPγ[S] , or PIP2 and GTPγ[S]. The activating effects of GTP and ATP were abolished by neomycin, a PIP2 scavenger. These results suggest that phospholipase D is regulated by GTP-binding protein and the presence of PIP2 is required for the activation induced by GTP. Protein kinase A may be another protein kinase in addition to protein kinase C and protein tyrosine kinase which regulate the activity of phospholipase D, when the intracellular concentration of cAMP is increased.

Journal

Molecular and Cellular BiochemistrySpringer Journals

Published: Oct 9, 2004

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