Document Detail


Hepatic monoacylglycerol acyltransferase is regulated by sn-1,2-diacylglycerol and by specific lipids in Triton X-100/phospholipid-mixed micelles.
MedLine Citation:
PMID:  8175745     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The lipid cofactor requirement of hepatic monoacylglycerol acyltransferase (MGAT) (EC 2.3.1.22) was studied in Triton X-100/lipid-mixed micelles. Anionic phospholipids and anionic lysophospholipids stimulated MGAT activity, whereas fatty acids and sphingosine inhibited enzyme activity. Phosphatidic acid was a potent activator, stimulating MGAT 11-fold at 4.2 mol %. Kinetic studies revealed that phosphatidic acid, with an apparent Ka of 0.26 mol %, was a better activator than phosphatidylserine, phosphatidylinositol, or cardiolipin. Of the anionic lysophospholipids, lysophosphatidic acid was a better activator than lysophosphatidylserine, stimulating maximally at less than 3 mol %. Oleate was a more potent inhibitor (Ki, 2.4 mol %) than sphingosine (Ki, 18.3 mol %). The dependence of MGAT on sn-2-monoacylglycerol was not cooperative in the absence or presence of anionic phospholipids, oleic acid, or sphingosine. The apparent Km for sn-2-monoC18:1-glycerol was 1.24 mol % in the presence of maximally activating phospholipid and 0.19 mol % when phospholipid was omitted. MGAT's product sn-1,2-diacylglycerol was a weaker activator than the anionic phospholipids, but the effects of diacylglycerol and phospholipid were additive. Activation by sn-1,2-diC18:1-glycerol was highly cooperative with a Hill coefficient of 3.6. Activation was specific for the sn-1,2-stereoisomer; neither 1,3-diacylglycerol nor the ether analogs of sn-1,2- or 1,3-diacylglycerol were activators. Since several of the lipid modulators of MGAT activity are intracellular second messengers, these data suggest the possibility that regulatory links exist between signal transduction and the synthesis of complex lipids via the monoacylglycerol pathway.
Authors:
B G Bhat; P Wang; R A Coleman
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  269     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1994 May 
Date Detail:
Created Date:  1994-06-09     Completed Date:  1994-06-09     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  13172-8     Citation Subset:  IM    
Affiliation:
Department of Nutrition, University of North Carolina, Chapel Hill 27599-7400.
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MeSH Terms
Descriptor/Qualifier:
Acyltransferases / antagonists & inhibitors,  metabolism*
Animals
Detergents
Diglycerides / metabolism*
Fatty Acids / pharmacology
Female
Kinetics
Lipids / pharmacology*
Liver / enzymology*
Micelles
Octoxynol
Phospholipids / metabolism*
Pregnancy
Rats
Rats, Sprague-Dawley
Sphingosine / pharmacology
Grant Support
ID/Acronym/Agency:
HD 19068/HD/NICHD NIH HHS
Chemical
Reg. No./Substance:
0/1,2-diacylglycerol; 0/Detergents; 0/Diglycerides; 0/Fatty Acids; 0/Lipids; 0/Micelles; 0/Phospholipids; 123-78-4/Sphingosine; 9002-93-1/Octoxynol; EC 2.3.-/Acyltransferases; EC 2.3.1.22/2-acylglycerol O-acyltransferase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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