| Evidence for the regulation of guinea-pig heart microsomal phosphatidylcholine-hydrolysing phospholipase A1 by guanosine 5'-[gamma-thio]triphosphate. | |
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MedLine Citation:
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PMID: 1472009 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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We have recently characterized lysophospholipase A2 activities in guinea-pig heart microsomes and postulated that these enzymes act sequentially with phospholipases A1 to release fatty acids selectively from phosphatidylcholine (PC) and phosphatidylethanolamine, thus providing an alternative route to the phospholipase A2 mode of release. In a further investigation of the postulated pathway, we have characterized the PC-hydrolysing phospholipase A1 in guinea-pig heart microsomes. Our results show that the enzyme may have a preference for substrates with C16:0 over C18:0 at the sn-1 position. In addition, although the enzyme cleaves the sn-1 fatty acid, the rate of hydrolysis of PC substrates with C16:0 at the sn-1 position was influenced by the nature of the fatty acid at the sn-2 position. The order of decreasing preference was C18:2 > C20:4 = C18:1 > C16:0. The hydrolyses of the molecular species were differentially affected by heating at 60 degrees C. An investigation into the effect of nucleotides on the activity of the enzyme showed that guanosine 5'-[gamma-thio]triphosphate (GTP[S]) inhibited the hydrolysis of PC by phospholipase A1 activity, whereas GTP, guanosine 5'-[beta-thio]diphosphate (GDP[S]), GDP, ATP and adenosine 5'-[gamma-thio]triphosphate (ATP[S]) did not affect the activity. The inhibitory effect of GTP[S] on phospholipase A1 activity was blocked by preincubation with GDP[S]. A differential effect of GTP[S] on the hydrolysis of different molecular species was also observed. Taken together, the results of this study suggest the presence of more than one phospholipase A1 in the microsomes with different substrate specificities, which act sequentially with lysophospholipase A2 to release linoleic or arachidonic acid selectively from PC under resting conditions. Upon stimulation and activation of the G-protein, the release of fatty acids would be inhibited. |
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Authors:
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K Badiani; X Lu; G Arthur |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: The Biochemical journal Volume: 288 ( Pt 3) ISSN: 0264-6021 ISO Abbreviation: Biochem. J. Publication Date: 1992 Dec |
Date Detail:
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Created Date: 1993-01-28 Completed Date: 1993-01-28 Revised Date: 2010-09-07 |
Medline Journal Info:
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Nlm Unique ID: 2984726R Medline TA: Biochem J Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 965-8 Citation Subset: IM |
Affiliation:
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Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada. |
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Detergents / pharmacology Fatty Acids / metabolism Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology* Guinea Pigs Hydrolysis Microsomes / enzymology Myocardium / enzymology* Phosphatidylcholines / metabolism* Phospholipases A / antagonists & inhibitors, metabolism* Phospholipases A1 Phospholipases A2 Phospholipids / metabolism Substrate Specificity Swine |
| Chemical | |
Reg. No./Substance:
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0/Detergents; 0/Fatty Acids; 0/Phosphatidylcholines; 0/Phospholipids; 37589-80-3/Guanosine 5'-O-(3-Thiotriphosphate); EC 3.1.1.-/Phospholipases A; EC 3.1.1.32/Phospholipases A1; EC 3.1.1.4/Phospholipases A2 |
| Comments/Corrections | |
Erratum In:
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Biochem J 1993 Jun 15;292(Pt 3):952 |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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