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)

Rat liver homogenate or cell fractions deacylate 12-O-tetradecanoyl phorbol 13-acetate (TPA) in vitro mainly by conversion to phorbol 13-acetate. The highest specific activity is located in the microsomal fraction. The deacylation is inhibited by bis-(4-nitrophenyl) phosphate, a selective inhibitor of nonspecific carboxylesterases. Only two of five purified esterases from rat liver endoplasmic reticulum deacylate TPA. These two esterases have formerly been characterized as acylcarnitine hydrolases and the more active one is also a potent diacylglycerol lipase. Its TPA-hydrolyzing activity is inhibited by other substrates like 1-naphthylacetate, lauroylcarnitine, or dioleoyl glycerol. The results support the view that phorbol esters act like structural analogs of diacylglycerols, not only with respect to their activating effect on protein kinase C, but also as substrates for the same lipases.
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PMID:The tumor promoter 12-O-tetradecanoyl phorbol 13-acetate and regulatory diacylglycerols are substrates for the same carboxylesterase. 371 Nov 10

The separation of rat epididymal adipocytes into plasma-membrane, mitochondrial, microsomal and cytosol fractions is described. The fractions, which were characterized by marker-enzyme analysis and electron-micrographic observation, from the cells of fed and 24 h-starved animals were used to prepare acetone/diethyl ether-dried powders for the measurement of lipoprotein lipase activities. The highest specific activities and proportion of recovered lipoprotein lipase activity were found in the plasma-membrane and microsomal fractions. The two fractions from the cells of fed rats showed similar activities and enrichments of the enzyme, these activities being higher than the plasma-membrane and lower than the microsomal activities recovered from the cells of starved animals. Chicken and guinea-pig anti-(rat lipoprotein lipase) sera were prepared, and an indirect labelled-second-antibody cellular immunoassay, using 125I-labelled rabbit anti-(chicken IgG) or 125I-labelled sheep anti-(guinea-pig IgG) antibodies respectively, for the detection of cell-surface enzyme was devised and optimized. The amount of immunodetectable cell-surface lipoprotein lipase was higher for cells isolated from fed animals than for cells from 24 h-starved animals, when either anti-(lipoprotein lipase) serum was used in the assay. The amount of immunodetectable cell-surface lipoprotein lipase fell further when starvation was extended to 48 h. The lipoprotein lipase of plasma-membrane vesicles was shown to be a patent activity and to be immunodetectable in a modification of the cellular immunoassay. Although the functional significance of the adipocyte surface lipoprotein lipase is not known, the possibility of it forming a pool of enzyme en route to the capillary endothelium is advanced.
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PMID:The lipoprotein lipase of white adipose tissue. Studies on the intracellular distribution of the adipocyte-associated enzyme. 379 91

A neutral triacylglycerol lipase activity that is separate and distinct from lipoprotein lipase (LPL) could be measured in homogenates of myocardial cells if protamine sulphate and high concentrations of albumin were included in the assay. This neutral lipase was predominantly particulate, with the highest relative specific activity in microsomal subcellular fractions. The induction of diabetes by the administration of streptozotocin to rats resulted in a decrease in LPL activity in myocyte homogenates and in particulate subcellular fractions, but the percentage of cellular LPL activity that was released during incubation of myocytes with heparin was normal. In contrast, neutral lipase activity was increased in diabetic myocyte homogenates and microsomal fractions. Acid triacylglycerol lipase activity was not changed in diabetic myocytes. The decrease in LPL in myocytes owing to diabetes may result in the decreased functional LPL activity at the capillary endothelium of the diabetic heart.
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PMID:Effect of diabetes on acid and neutral triacylglycerol lipase and on lipoprotein lipase activities in isolated myocardial cells from rat heart. 380 Sep 35

The lipolytic activities of heart tissue towards full and partial acylglycerols were characterized. Tissue lysosomal, acid lipase activity (pH 4.8) was inhibited by high salt, protamine sulfate, NaF, MgATP, Triton X-100, serum and the esterase-inhibitor diethylparanitrophenyl phosphate. The tissue neutral triacylglycerol lipase activity (pH 7.4) was recovered predominantly in the microsomal and soluble fractions and exhibited essentially identical properties towards activators (serum, apolipoprotein C-II) and reagents (NaCl, Triton X-100, NaF, MgATP and diethylparanitrophenyl phosphate) relative to vascular lipoprotein lipase, except for protamine sulfate which increased the serum-stimulated neutral triacylglycerol lipase activity. Triacylglycerol hydrolysis at acid pH was incomplete, whereas at neutral pH full hydrolysis occurred. Myocardial mono- and diacylglycerol lipase activities, with pH optima of 8.0 and 7.4, respectively, were recovered in the microsomal fraction. They differed immunologically from neutral lipase and lipoprotein lipase and did not bind to heparin-Sepharose 4B. They were kinetically different, partially inhibited by NaCl and differentially affected by protamine sulfate. NaF, Triton X-100 and diethylparanitrophenyl phosphate. Our data suggest that endogenous hydrolytic activity against full and partial acylglycerols is mediated by separate enzymes.
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PMID:Characterization of mono-, di- and triacylglycerol lipase activities in the isolated rat heart. 394 May 38

Rat hearts were depleted in vivo from both the heparin-releasable lipoprotein lipase and heparin-resistant tissue neutral triacylglycerol lipase activity by treatment of the animals with cycloheximide (2 mg/kg body weight), intraperitoneally injected 2.5 and 5 h prior to perfusion. The tissue acid lipase, mono- and diacylglycerol lipase activities were not affected by cycloheximide-induced inhibition of protein synthesis. Myocardial basal and glucagon-stimulated lipolysis, determined by the rate of glycerol production and release from the isolated hearts, was not significantly different in control and cycloheximide-treated rats. Tissue triacylglycerols were recovered with the highest relative specific distribution in the lysosomal fraction isolated from heart homogenates. Upon prolongation of the perfusion-duration the relative specific distribution of triacylglycerols in the lysosomal fraction decreased. In addition, the specific lysosomal triacylglycerol content (micrograms/mg protein) dropped significantly, indicating an important role of lysosomes in myocardial triacylglycerol turnover. Our data strongly suggest that the heparin-resistant neutral triacylglycerol lipase activity may not be the only determinant of endogenous lipolysis in the isolated rat heart and indicate that lipolysis may additionally be mediated by the lysosomal, acid lipase in concert with the microsomal mono-and diacylglycerol lipase.
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PMID:Studies on the involvement of lipolytic enzymes in endogenous lipolysis of the isolated rat heart. 394 May 39

1. A rat brain supernatant and microsomal fraction contained a phospholipase A1 enzyme which hydrolysed phosphatidylinositol at pH 8 in the absence of calcium. Triolein and phosphatidylcholine were not attacked under the same incubation conditions. 2. No evidence could be obtained for a phospholipase A2 in the microsomal preparation, and in the presence of Ca2+ the release of fatty acid observed was due to phosphatidylinositol phosphodiesterase followed by diacylglycerol lipase action. 3. Brain phosphatidylinositol phosphodiesterase showed extensive activity in the alkaline range (7-8.5) as well as at pH 5-5.5. The activity at higher pH values required higher calcium concentrations and disappeared on purification of the soluble enzyme by ammonium sulphate fractionation. 4. In general the ratio between inositol 1,2-(cyclic)phosphate and inositol 1-phosphate produced by phosphodiesterase action decreased with increasing pH.
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PMID:The catabolism of phosphatidylinisitol by an EDTA-insensitive phospholipase A1 and calcium-dependent phosphatidylinositol phosphodiesterase in rat brain. 627 69

1. The effects of dietary modification, including starvation, and of corticotropin injection on the activities of acyl-CoA synthetase, glycerol phosphate acyltransferase, dihydroxyacetone phosphate acyltransferase, phosphatidate phosphohydrolase, diacylglycerol acyltransferase and lipoprotein lipase were measured in adipose tissue. 2. Lipoprotein lipase activities in heart were increased and those in adipose tissue were decreased when rats were fed on diets enriched with corn oil or beef tallow rather than with sucrose or starch. The lipoprotein lipase activity was lower in the adipose tissue of rats fed on the sucrose rather than on the starch diet. 3. Rats fed on the beef tallow diet had slightly higher activities of the total glycerol phosphate acyltransferase in adipose tissue than did rats fed on the sucrose or starch diet. The diacylglycerol acyltransferase and the mitochondrial glycerol phosphate acyltransferase activities were higher for the rats fed on the tallow diet than for those fed on the corn-oil diet. 4. Starvation significantly decreased the activities of lipoprotein lipase (after 24 and 48 h), acyl-CoA synthetase (after 24 h) and of the mitochondrial glycerol phosphate acyltransferase and the N-ethylmaleimide-insensitive dihydroxyacetone phosphate acyltransferase (after 48 h) in adipose tissue. The activities of the microsomal glycerol phosphate acyltransferase, diacylglycerol acyltransferase and the soluble phosphatidate phosphohydrolase were not significantly changed after 24 or 48 h of starvation. 5. The activities of lipoprotein lipase and phosphatidate phosphohydrolase in adipose tissue were decreased 15 min after corticotropin was injected into rats during November to December. No statistically significant differences were found when these experiments were performed during March to September. These differences may be related to the seasonal variation in acute lipolytic responses. 6. These results are discussed in relation to the control of triacylglycerol synthesis and lipoprotein metabolism.
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PMID:The activities of lipoprotein lipase and of enzymes involved in triacylglycerol synthesis in rat adipose tissue. Effects of starvation, dietary modification and of corticotropin injection. 628 Jun 82

Mobilization of triacylglycerol stored in heart cells is accomplished by the combined action of lysosomal (acid) lipase and microsomal monoacylglycerol lipase or carboxylesterase. Non(heparin)-releasable neutral or alkaline lipase is similar to non(readily)-releasable lipoprotein lipase (LPL). The enzyme is mainly localized extracellularly. Non(readily)-releasable LPL probably represents LPL in caveola or vacuolae of vascular endothelium and/or LPL on myocardial interstitium. It contributes to the uptake of lipoprotein constituents in heart cells. Glycerol, an endproduct of lipolysis, is not a reliable marker for the net mobilization of lipid stored in heart cells. It is formed both intra- and extracellularly, and does not reflect the rate of oxidation of part of free fatty acids formed.
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PMID:Localization and function of myocardial lipolysis. 647 80

The characteristics of acid esterase from the patient with Wolman's disease, a rare familial lipidosis, were studied. Enzymatic analysis as well as mineral analysis were performed on the patient's liver, spleen, and adrenal glands. Acid esterase was low in the patient's leucocytes and other affected tissues. Further enzymatic study with subcellular fractions of the liver in both patient and control subject revealed that acid esterase was mostly localized in the membrane of lysosomes. The lysosomal esterase was unaffected by Ca2+, Mg2+, EDTA, E600 (microsomal esterase inhibitor), and it was less inhibited by NaCl than other fractions. Studies with those inhibitors showed that acid esterase has different properties compared to other lipases, such as lipoprotein lipase, adipose tissue lipase, and hepatic microsomal lipase. Studies with inhibitors also gave a negative view on a possible suppressive interaction of the high content of calcium in the target organs with acid esterase in Wolman's disease.
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PMID:Characteristics of acid esterase in Wolman's disease. 651 76

The lipid-lowering effect of pantethine, a new drug affecting lipid metabolism, had been evaluated in carbohydrate-induced hyperlipidemic rats. Administration of the drug raised post-heparin lipolytic activities, the change being due to an increase in lipoprotein lipase activity, whereas hepatic lipase activity remained virtually unchanged. Total lipoprotein lipase activity per g of adipose tissue increased in pantethine-treated rats compared with controls. Furthermore, the soluble lipoprotein lipase of fat-pads was fractionated by heparin-Sepharose affinity chromatography. The first active peak, originated from the microsomal fractions, significantly increased after the drug treatment, while the second one, originated from the plasma membranes, remained unchanged. The increase in the microsomal lipoprotein lipase activity may be due to an increase in intracellular synthesis of lipoprotein lipase enzyme proteins. The heterogeneity of lipoprotein lipase of rat adipose tissues was ensured using affinity chromatography on heparin-Sepharose.
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PMID:Effect of pantethine on post-heparin plasma lipolytic activities and adipose tissue lipoprotein lipase in rats. 673 46


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