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Chylomicron catabolism is known to be initiated by the enzyme lipoprotein lipase (triacylglycero-protein acylhydrolase, EC 3.1.1.34). Chylomicron remnants, produced by lipolysis, are rapidly taken up by the liver via an apolipoprotein E (apoE)-mediated, receptor-dependent process. The low density lipoprotein (LDL) receptor-related protein (LRP) has been(More)
Lipoprotein lipase and hepatic lipase were measured in rat plasma using specific antisera. Mean values for lipoprotein lipase in adult rats were 1.8-3.6 mU/ml, depending on sex and nutritional state. Values for hepatic lipase were about three times higher. Lipoprotein lipase activity in plasma of newborn rats was 2-4-times higher than in adults. In(More)
To explore how enzyme affinities and enzyme activities regulate hydrolysis of water-insoluble substrates, we compared hydrolysis of phospholipid-stabilized emulsions of medium-chain (MCT) versus long-chain triacylglycerols (LCT). Because substrate solubility at the emulsion surface might modulate rates of hydrolysis, the ability of egg yolk(More)
To determine whether an apolipoprotein-free artificial triacylglycerol emulsion can substitute for VLDL in studying cholesterol ester-triacylglycerol exchange processes between triacylglycerol-rich lipoproteins and cholesterol ester-rich lipoproteins, we used Intralipid to modify human plasma LDL. Intralipid was incubated with LDL in the presence of(More)
In this study, we have investigated the effects of alimentary lipemia in 15 normotriglyceridemic individuals on high density lipoproteins2 (HDL2) with respect to structure, composition, and substrate efficacy for hepatic lipase in vitro. In the study subjects, HDL2 levels ranged widely from 4.7 to 151.7 mg/dl plasma. HDL2 were isolated in the postabsorptive(More)
The lipolysis of rat chylomicron polyenoic fatty acid esters with bovine milk lipoprotein lipase and human hepatic lipase was examined in vitro. Chylomicrons obtained after feeding fish oil or soy bean oil emulsions were used as substrates. The lipolysis was followed by gas chromatography or by using chylomicrons containing radioactive fatty acids.(More)
To explore the interactions of triacylglycerol and phospholipid hydrolysis in lipoprotein conversions and remodeling, we compared the activities of lipoprotein and hepatic lipases on human VLDL, IDL, LDL, and HDL2. Triacylglycerol and phospholipid hydrolysis by each enzyme were measured concomitantly in each lipoprotein class by measuring hydrolysis of(More)
Lipoprotein lipase (LPL) is rapidly and efficiently cleared from the circulation by the liver through an as yet unclear mechanism. In the present study, we determined the nature of LPL interactions with the liver parenchimal cell line HepG2 as compared to other cells in culture. Binding, cell association and degradation of 125I-labelled bovine milk LPL by(More)
Lipoprotein lipase (LPL) catalyzes the flux-generating step in transport of fatty acids from lipoprotein triacylglycerols into tissues for use in metabolic reactions. In vitro studies have shown that fatty acids can bind to the enzyme and impede its other interactions. In this study we have searched for evidence of fatty acid control of LPL in vivo by rapid(More)
This study was designed to further ascertain the presence in plasma of lipoprotein lipase (LPL) bound to circulating lipoproteins. Lipoprotein lipase mass and activity values in preheparin plasma from 20 volunteers were 69.8 +/- 6.6 ng.ml-1 and 1.54 +/- 0.15 mU.ml-1, respectively, and no significant correlation between mass and activity was observed.(More)