ISSN:
1573-4919
Keywords:
phospholipase D
;
human hepatocarcinoma cell line
;
adenine guanine nucleotides
;
protein kinase A
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007065408099
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