ISSN:
0263-6484
Keywords:
Lipoprotein lipase
;
diester lipase
;
monoeser lipase
;
oleic acid uptake
;
cell lipids
;
apolipoproteins
;
female rats
;
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Extracellular acylglycerols are hydrolysed by lipases active at the surface of intact fat cells isolated from rat or human adipose tissue. During short-term incubation, rat fat cells hydrolyse di-[3H]oleyl-[14C]glycerol at a rate of 70 ± 7·7 mU/106 cells (means ± S.E.) versus 440 ± 62 mU/106 cells for the hydrolysis of mono-[3H]oleylglycerol; these relatively high lipolytic potencies may serve, among other functions, to counteract the cytolytic effect of both esters. Reaction rates with both substrates are unchanged by addition of various apolipoproteins C and by the nutritional state of the animals. Fat cells incorporate 15-20 per cent of the total [3H]-oleic chains liberated by hydrolysis, with no correlation between uptake and hydrolysis rates. [3H]-oleic chains in cell lipids are found mainly as diacylglycerol (15 per cent) and triacylglycerol (80 per cent). Both lipolytic processes differ from the hydrolysis of trioleyglycerol by cell-bound lipoprotein lipase, which occurs at lower rates (6·5 ± 0·6 mU/106 cells) and depends on apolipoprotein C-II and nutritional state of the animals. The results support the accepted view that lipoprotein lipase and monoacylglycerol lipase are distinct enzymes. Differences between lipoprotein lipase and diacylglycerol lipase activities raise the possibility of different catalytic entities. In conclusion, isolated fat cells in suspension hydrolyse and incorporate lipids. This model should approximate physiological conditions more closely than the use of lipases in the free state.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cbf.290050304
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