Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.34 (lipoprotein lipase)
7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the hawkmoth Manduca sexta high density lipophorin from adult insects (HDLp-A) delivers lipids to developing oocytes. During this lipid delivery HDLp-A is taken up by the oocyte and converted to a very high density lipophorin (VHDLp), which is stored in protein storage granules (yolk bodies). A membrane-free lysate of isolated M. sexta yolk bodies was demonstrated to contain lipoprotein lipase activity that hydrolyses the diacylglycerol of HDLp-A. With HDLp-A as a substrate yolk body lipophorin lipase (YBLpL) activity was shown to be maximal between pH 9 and pH 9.5. NaCl concentration was optimal between 0.7 M and 1 M. YBLpL activity required neither bovine serum albumin nor calcium ions but appeared to be stimulated by 5 mM EDTA. Diisopropyl fluorophosphate effectively inhibited YBLpL activity, indicating the presence of a serine in the active site of the enzyme. The identified lipase activity co-eluted with lipophorins and vitellins from the yolk in the void volume of a Sephadex G-75 gel filtration column. This observation suggests that the lipase has a Mr of more than 80,000, or that the enzyme is associated with the lipoproteins. Incubation of HDLp-A with yolk body lysate converted HDLp-A to two classes of higher density lipophorins. The highest density lipophorins produced during this incubation approached the density of VHDLp as it is isolated from mature eggs. The possible role of YBLpL activity in the delivery of lipids to developing oocytes is discussed.
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PMID:Lipophorin lipase from the yolk of Manduca sexta eggs: identification and partial characterization. 162 20

Diacylglycerol lipase (glycerol ester hydrolase, EC 3.1.1.3) activities were investigated in subcellular fractions from neonatal and adult rat liver in order to determine whether one or more different lipases might provide the substrate for the developmentally expressed, activity monoacylglycerol acyltransferase. The assay for diacylglycerol lipase examined the hydrolysis of sn-1-stearoyl,2- [14C]oleoylglycerol to labeled monoacylglycerol and fatty acid. Highest specific activities were found in lysosomes (pH 4.8) and cytosol and microsomes (pH 8). The specific activity from plasma membrane from adult liver was 5.8-fold higher than the corresponding activity in the neonate. In other fractions, however, no developmental differences were observed in activity or distribution. In both lysosomes and cytosol, 75 to 90% of the labeled product was monoacylglycerol, suggesting that these fractions contained relatively little monoacylglycerol lipase activity. In contrast, 80% of the labeled product from microsomes was fatty acid, suggesting the presence of monoacylglycerol lipase in this fraction. Analysis of the reaction products strongly suggested that the lysosomal and cytosolic diacylglycerol lipase activities hydrolyzed the acyl-group at the sn-1 position. The effects of serum and NaCl on diacylglycerol lipase from each of the subcellular fractions differed from those effects routinely observed on lipoprotein lipase and hepatic lipase, suggesting that the hepatic diacylglycerol lipase activities were not second functions of these triacylglycerol lipases. Cytosolic diacylglycerol lipase activity from neonatal liver and adult liver was characterized. The apparent Km for 1-stearoyl,2-oleoylglycerol was 115 microM. There was no preference for a diacylglycerol with arachidonate in the sn-2 position. Bovine serum albumin stimulated the activity, whereas dithiothreitol, N-ethylmaleimide, and ATP inhibited the activity. Both sn-1(3)- and 2-monooleylglycerol ethers stimulated cytosolic diacylglycerol lipase activity 2-3-fold. The corresponding amide analogs stimulated 28 to 85%, monooleoylglycerol itself had little effect, and 1-alkyl- or 1-acyl-lysophosphatidylcholine inhibited the activity. These data provide the first characterization of hepatic subcellular lipase activities from neonatal and adult rat liver and suggest that independent diacylglycerol and monoacylglycerol lipase activities are present in microsomal membranes and that the microsomal and cytosolic diacylglycerol lipase activities may describe an ambipathic enzyme. The data also suggest possible cellular regulation by monoalkylglycerols.
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PMID:Diacylglycerol metabolism in neonatal rat liver: characterization of cytosolic diacylglycerol lipase activity and its activation by monoalkylglycerols. 163 59

To assess the mechanism of serum lipoprotein abnormalities in continuous ambulatory peritoneal dialysis (CAPD), we measured serum lipids, apolipoproteins, and postheparin lipases in 46 patients with end-stage renal disease (ESRD) treated on CAPD, 26 patients on hemodialysis (HD), and 29 healthy subjects. HD patients had higher serum triglyceride levels than the healthy controls, showing type IV and type III phenotypes. They had significantly lower activities of hepatic triglyceride lipase (HTGL) in postheparin plasma compared with controls, and postheparin lipoprotein lipase (LPL) was also decreased by 15%, although the latter change was not statistically significant. CAPD patients had elevated levels in triglyceride, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and apolipoprotein (apo) B, showing type IV, III, and II (IIb and IIa) phenotypes. The mean LPL and HTGL activities in CAPD patients were not different from those of HD patients. CAPD patients with hyperlipoproteinemia had significantly higher serum albumin levels than those with normolipidemia. There was a significant positive correlation between albumin and apo B levels in CAPD patients. In hyperlipidemic CAPD patients, there was no difference in serum albumin concentrations or HTGL activities among lipoprotein phenotypes, whereas LPL activities were significantly higher in the patients with type II than those with type IV hyperlipoproteinemia. These results suggest that there was some linkage between alterations in serum albumin and lipoproteins, and that LPL was related to phenotypic variation of hyperlipoproteinemia in CAPD.
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PMID:Roles of hypoalbuminemia and lipoprotein lipase on hyperlipoproteinemia in continuous ambulatory peritoneal dialysis. 194 24

The sequential lipolysis of trioleoylglycerol and the triacylglycerols of very-low-density lipoprotein by bovine milk lipoprotein lipase can be described by the consecutive reactions: (formula: see text) where k'1, k'2 and k'3 are apparent first-order rate constants. The values of these rate constants dictate several conclusions concerning the reaction mechanism of this enzyme. The significant differences in the k'1, k'2 and k'3 values for trioleoylglycerol substrate imply that cleavage of the acyl-enzyme intermediate is not the rate-limiting step of the overall lipolysis reaction. This conclusion is further supported by the lack of an effect of hydroxylamine on the reaction rate. In addition, the observed isotope effect of k1 (H2O): k1(D2O) of 1.32 with trioleoylglycerol substrate suggests that the acyl-enzyme formation may contribute to the rate-limiting step of the lipoprotein-lipase-catalyzed reaction. In the presence of excess bovine serum albumin, the transfer of fatty acid product from the enzyme to albumin must be fast, since the k'1 values are not dependent on albumin concentration. When albumin is not in excess, the reaction is retarded and the study of reaction kinetics demonstrates negligible reaction after the available albumin is saturated.
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PMID:Acylglycerol reactivity and reaction mechanism of bovine milk lipoprotein lipase. 231 24

It has been established previously that nephrotic hyperlipidemia is characterized by both an increase in lipid synthesis and a defect in removal of lipoproteins. The relationship between these defects and altered albumin metabolism is uncertain. One hypothesis is that hepatic lipogenesis increases in parallel with albumin synthesis. To test this hypothesis, albumin synthesis was increased in nephrotic rats fed an 8.5% protein diet (LPN) by increasing dietary protein to 40% (HPN). Proteinuria was modulated in half of the rats fed 40% protein by enalapril (HPE). Albumin synthesis was the same in both HPN and HPE, but proteinuria was reduced in HPE compared to HPN, and so were serum cholesterol and triglycerides (TG). To examine the effect of serum albumin on lipid clearance in the absence of proteinuria, plasma clearance of chylomicrons (CM) and VLDL was measured in Nagase analbuminemic rats (NAR) and found to be no different than in normal SD rats. When proteinuria was induced in NAR and in SD rats, a severe and identical defect in both CM and VLDL clearance was acquired in both groups and blood lipid levels were increased to a similar degree in both groups. Neither hyperlipidemia nor defective removal of lipoproteins from the circulation are linked to albumin synthesis or serum albumin concentration but result, at least in part, from proteinuria. Postheparin lipoprotein lipase (LPL) activity was reduced slightly in nephrotic animals compared to nonnephrotic controls, but the most striking finding was a highly significant decrease in postheraprin LPL activity in normal NAR compared to SD rats (P less than 0.001), suggesting that reduced LPL activity is not responsible for reduced clearance of CM and VLDL in nephrotic rats.
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PMID:Proteinuria, not altered albumin metabolism, affects hyperlipidemia in the nephrotic rat. 238 6

The effects of ligand binding to the scavenger receptor on the secretion of lipoprotein lipase by murine macrophages were examined. Inflammatory macrophages exposed to acetylated low-density lipoprotein (AcLDL) exhibited a dose-dependent, 40-80% increase in lipoprotein lipase secretion. This stimulation appeared to be unrelated to intracellular cholesterol and triacylglycerol levels and to phagocytosis in general. Resident and inflammatory macrophages treated with maleylated bovine serum albumin (Mal-BSA) showed a 3-fold increase in lipoprotein lipase secretion in a dose-dependent and time-dependent fashion. In contrast, dextran sulfate, which is another ligand recognized by the scavenger receptor, caused a dose-dependent decrease in lipoprotein lipase secretion. Casein, a ligand recognized by the Mal-BSA receptor, did not affect lipoprotein lipase secretion nor the ability of Mal-BSA to stimulate the enzyme, while dextran sulfate abolished the stimulatory effects of Mal-BSA. Since ethylamine, an inhibitor of receptor-mediated endocytosis, attenuated the increase in lipoprotein lipase secretion induced by AcLDL and Mal-BSA, but did not affect the inhibition induced by dextran sulfate, it is suggested that receptor-mediated endocytosis of ligands via the scavenger receptor might play a key role in the stimulation of lipoprotein lipase secretion in macrophages. This study reveals another mechanism for regulation of macrophage lipoprotein lipase secretion.
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PMID:Regulation of macrophage lipoprotein lipase secretion by the scavenger receptor. 317 35

The lipase activity of the adult rat heart consists of at least two components; a lipoprotein lipase and a "hormone-sensitive" or triglyceride lipase. The control of the triglyceride lipase by intermediates of lipid metabolism was studied in rat heart homogenates. Perfusion of hearts with fatty acids, glucose or no exogenous substrate did not alter lipase activity. Bovine serum albumin (BSA) stimulated the in vitro lipase activity whereas palmityl-coenzyme A (CoA) was a potent inhibitor. Other fatty acid intermediates such as acetyl-CoA, acetyl-carnitine, palmityl-carnitine and palmitate had little or no effect. Long-chain acyl CoA may be an important intermediate for matching triglyceride hydrolysis with the supply of extracellular fatty acids and the rates of fatty acid oxidation.
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PMID:Inhibition of myocardial lipase by palmityl CoA. 341 15

The effects of bovine serum albumin on rat pancreatic lipase and bovine milk lipoprotein lipase were studied in a system of triacylglycerol emulsions stabilized by 1 1 mg/ml albumin. At concentrations greater than 1 mg/ml, albumin inhibited the activity of pancreatic lipase and interfered with enzyme binding to emulsified triacylglycerol particles. These effects could be countered by occupying five fatty acid binding sites on albumin with oleic acid. Following an initial lag period which increased with albumin concentrations, enzyme activity escaped from inhibition presumably due to saturation of fatty acid sites on albumin with oleic acid. Pancreatic lipase was active at 1 mg/ml albumin and 1 mM emulsion-bound oleic acid in the system. The effects of albumin on lipoprotein lipase were diametrically opposed to the above; enzyme activity was completely inhibited by 0.1 mM oleic acid, it increased with increasing fatty acid-free albumin concentrations and decreased as the fatty acid sites on albumin were filled. At 1 mM oleic acid and no added albumin the enzyme failed to bind at the oil water interface, whereas fatty acid-free or saturated albumin had no effect on binding. It is concluded that if the inhibition of pancreatic lipase by albumin is due to the inaccessibility of the enzyme to an oil-water interface blocked by denatured albumin, then albumin saturated with oleic acid would seem to be protected from unfolding at the interface and more readily displaced by the lipase. Pancreatic lipase and lipoprotein lipase, although sharing a number of common features, are distinct enzymes both functionally and mechanistically.
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PMID:The effects of bovine serum albumin and oleic acid on rat pancreatic lipase and bovine milk lipoprotein lipase. 360 28

Lipoprotein lipase [EC 3.1.1.34, LpL] was purified from human postheparin plasma (PHP) almost to homogeneity (a 210,000-fold purification) using columns of heparin-Sepharose, hydroxylapatite, and concanavalin A-Sepharose, and its properties were compared with the purified bovine milk LpL. The specific activity of the PHP-LpL was 26 mmol free fatty acids (FFA)/h/mg of protein at 37 degrees C; close to that of bovine milk LpL (35 mmol FFA/h/mg). For both enzyme preparations, the pH optimum (about 8.7) and the inhibition by sodium chloride were almost the same. The apparent Michaelis constants were also similar; 2.5 mM for human PHP-LpL and 2.1 mM for bovine milk LpL. The apparent molecular weight of the purified human PHP-LpL was 58,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, slightly larger than that of the bovine milk LpL (56,000). Although the amino acid composition of the two LpL preparations had only slight differences, antibody raised against bovine milk LpL cross-reacted very weakly with purified human PHP-LpL. With 1% bovine serum albumin, bovine milk LpL was highly stable, but the human PHP-LpL was unstable; it lost 60% of its activity within 60 min at 0 degrees C. In the absence of apolipoprotein C-II (apo C-II), the activity of human PHP-LpL was very weak. However, human PHP-LpL was activated by apo C-II more strongly than bovine milk LpL; the fold activation of human PHP-LpL by apo C-II was 7-8 times that of bovine milk LpL. The apparent Km value of human PHP-LpL for apo C-II (1.00 +/- 0.58 microM) was larger than that of bovine milk LpL (0.15 +/- 0.03 microM).
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PMID:Purification and characterization of lipoprotein lipase from human postheparin plasma and its comparison with purified bovine milk lipoprotein lipase. 378 53

A model system to study the putative role of cholesteryl ester transfer protein in the egress of interstitial cholesteryl ester is described. Confluent cultures of bovine aortic smooth muscle cells were labeled for 24 h with [3H]cholesteryl linoleyl ether and [14C]cholesteryl linoleate by incubation with bovine milk lipoprotein lipase. This method of labeling results in the transfer of cholesteryl linoleyl ether and cholesteryl ester to three compartments: a trypsin-releasable, trypsin-resistant and catabolic compartment (Stein, O., Halperin, G., Leitersdorf, E., Olivecrona, T. and Stein, Y. (1984) Biochim. Biophys. Acta 795, 47-59). The efflux of labeled cholesteryl linoleyl ether and cholesteryl ester from the extracellular and cell-surface related compartments into a serum-free culture medium containing 1% bovine serum albumin was studied during 24 h of postincubation. The efflux was expressed as a percentage of pulse value, i.e., radioactivity retained by the cell culture at the end of the labeling period. The efflux of [3H]cholesteryl linoleyl ether, [14C]cholesteryl ester and 14C-labeled free cholesterol (formed by cellular hydrolysis of cholesterol ester) into the culture medium with 1% bovine serum albumin was about 5% of the pulse value. Addition of human lipoprotein-deficient serum resulted in a 3-10-fold increase in the efflux of [3H]cholesteryl linoleyl ether and [14C]cholesteryl ester, but did not change markedly the efflux of 14C-labeled free cholesterol. Rat lipoprotein-deficient serum which does not contain cholesteryl ester transfer protein did not increase the efflux of [3H]cholesteryl linoleyl ether or [14C]cholesteryl ester. The rate of cholesteryl ester efflux in the presence of human lipoprotein-deficient serum was linear for about 6 h and increased further up to 24 h. Addition of Intralipid to medium containing human lipoprotein-deficient serum further enhanced the efflux of [3H]cholesteryl linoleyl ether and, to a lesser extent, that of cholesteryl ester. A similar effect was observed also by addition of rat VLDL to medium containing human lipoprotein-deficient serum. Inhibition of cholesteryl linoleyl ether and cholesteryl ester efflux and marked enhancement of free cholesterol efflux occurred when rat HDL was added to medium containing human lipoprotein-deficient serum, while human HDL was only slightly inhibitory. The results obtained with human lipoprotein-deficient serum were reproduced with partially purified cholesteryl ester transfer protein. Using the partially purified cholesteryl ester transfer protein, the efflux of cholesteryl linoleate was compared to that of cholesteryl oleate and was found to be the same.
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PMID:Putative role of cholesteryl ester transfer protein in removal of cholesteryl ester from vascular interstitium, studied in a model system in cell culture. 399 71


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