Document Detail

The influence of fatty acid unsaturation and physical properties of microsomal membrane phospholipids on UDP-glucuronyltransferase activity.
MedLine Citation:
PMID:  2499306     Owner:  NLM     Status:  MEDLINE    
The relationship between lipid composition, the physical properties of microsomal phospholipids and the kinetics of liver UDP-glucuronyltransferase was studied in microsomes from guinea pigs supplied with a normal or a fat-free diet for 28 days. Fatty acid deficiency did not modify either the cholesterol/phospholipid molar ratio or the polar head group composition, but exclusively redistributed the unsaturated fatty acid pattern, by partially exchanging oleic for linoleic acid. This phenomenon accounts for the decrease of both rotational and translational mobilities of the fluorescent probes 1,6-diphenyl-1,3,5-hexatriene (DPH) and pyrene respectively. When the thermotropic behaviour of the different systems was assessed, no transition temperature (gel-liquid-crystalline) between 10 and 40 degrees C was seen as a consequence of the lower degree of unsaturation, either in the microsomal membranes or in the total lipid or total phospholipid extracts from the treated animals. In spite of this, the polarization ratio of trans-parinaric acid and the fluorescence intensity of merocyanine 540 revealed that a significant lateral phase separation occurred at 20-22 degrees C in the extracted phospholipids, which was smoother in the total lipid fractions and in the native microsomal membranes. Fatty acid deficiency caused an upward shift of the midpoint temperature of the lateral phase separation. Furthermore, the phosphatidylcholine extracted from the 'normal' microsomes showed a lateral phase separation centred at a lower temperature than that extracted from 'fat-deficient' microsomes. In contrast, the Arrhenius plot of UDP-glucuronyltransferase from 'normal' microsomes exhibited a change in slope at a higher temperature than that from treated microsomes. These results would suggest that fatty acid deficiency in guinea-pig liver microsomes, while rigidizing the bulk lipids, would segregate the most unsaturated phosphatidylcholine molecules towards the UDP-glucuronyltransferase microenvironment, in accordance with our previous results with cholesterol incorporation [Castuma & Brenner (1986) Biochemistry 25, 4733-4738].
C E Castuma; R R Brenner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Biochemical journal     Volume:  258     ISSN:  0264-6021     ISO Abbreviation:  Biochem. J.     Publication Date:  1989 Mar 
Date Detail:
Created Date:  1989-06-27     Completed Date:  1989-06-27     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  2984726R     Medline TA:  Biochem J     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  723-31     Citation Subset:  IM    
Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CONICET-UNLP, Facultad de Ciencias Médicas, Argentina.
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MeSH Terms
Chemistry, Physical
Cholesterol / analysis
Fatty Acids, Unsaturated / analysis,  metabolism*
Glucuronosyltransferase / metabolism*
Guinea Pigs
Hot Temperature
Membrane Lipids / metabolism*
Microsomes, Liver / analysis,  enzymology*
Phospholipids / analysis,  metabolism*
Physicochemical Phenomena
Reg. No./Substance:
0/Fatty Acids, Unsaturated; 0/Membrane Lipids; 0/Phospholipids; 57-88-5/Cholesterol; EC

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