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)

Extracts of acetone-ether powders of bovine thoracic aorta contain lipase activity which has an alkaline pH maximum (7.8-8.4) and is stimulated 4-10-fold by adding serum or isolated apolipoprotein-glutamate to the assay mixture. Serum activation is completely reversed by isolated apolipoprotein-serine or apolipoprotein-alanine. Lipolysis is strongly inhibited by NaCl (0.5 M) and protamine sulfate (1 mg/ml) and partially inhibited by heparin. Based on these characteristics, the lipase is identified as lipoprotein lipase.
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PMID:Detection and partial characterization of lipoprotein lipase in bovine aorta. 0 Oct 87

In present study interactions of some adrenergic drugs with the binding of 3H-norepinephrine (NE) and response of some enzymatic systems in the heart of rats with pharmacological hyperthyroidism have been investigated. Binding of NE to cardiac particles was inhibited by isoproterenol, propranolol and in lower concentrations by another beta-blocking drug trimepranol both in control and hyperthyroid hearts in the same degree. However, after addition of nonradioactive norepinephrine (10(-3) M) the degree of displacement was lower in hyperthyroid than in euthyroid group. Activity of adenylate cyclase was lower in hyperthyroid cardiac particles. This difference remained preserved after stimulation by norepinephrine or NaF. The activities of hormone-sensitive lipase and lipoprotein lipase were increased in preparation of hyperthyroid hearts. The phosphorylase "a" activity was also increased in hyperthyroid cardiac particles. There was no change in cardiac adrenergic binding sites properties in hyperthyroidism with the exception of less displacement of NE by nonlabelled hormone. The results indicate that the increased lipolytic and phosphorylase "a" activities in hyperthyroid hearts are not necessarily linked to elevated activity of adenylate cyclase.
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PMID:Adrenergic binding sites and enzyme activities in the heart of hyperthyroid rats. 0 59

Several mammary and adipose enzymes were measured in normal, adrenal-ectomized, adrenalectomized cortisol-treated, and intake-restricted lactating rats. Acetyl-CoA carboxylase, lipoprotein lipase, and triglyceride synthetase complex activities in mammary tissue were unchanged by intake restriction, decreased by adrenalectomy, and increased by glucocorticoid-replacement therapy. Malic dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and lipoprotein lipase activities in adipose were unchanged after adrenalectomy.
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PMID:Effects of adrenalectomy and glucocorticoid therapy on enzyme activities in mammary and adipose tissues from lactating rats. 0 27

Lipolytic activity was measured under different conditions in isolated fat cells and homogenates of human adipose tissue of the greater omentum. It was demonstrated that lipolysis took place in isolated fat cells at an optimum pH of 7.4 and was markedly stimulated by noradrenaline, but not by blood serum. By contrast lipolysis was significantly stimulated by blood serum, but not by noradrenaline, in homogenates of adipose tissue. Serum-stimulated lipolysis exhibited optimum activity at pH 8 and was inhibited by 1M sodium chloride. It is concluded that lipolytic activity in isolated fat cells can mainly be ascribed to the action of hormone-sensitive lipase, whereas lipolysis in homogenates of adipose tissue in the presence of serum is mostly regulated by lipoprotein lipase.
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PMID:[Lipolysis in human adipose tissue (author's transl)]. 0 90

The effects of lipolysis on the structure of chylomicrons were studied with the scanning electron microscope using rat chylomicrons incubated with purified bovine milk lipoprotein lipase for 20 minutes at pH 8.1. Since the amount of albumin added to the medium was limited, some of the free fatty acids and partial glycerides formed by lipolysis accumulated in the chylomicrons. Lipolyzed chylomicrons fixed with OSO4 at pH 7.4 appeared in scanning electron micrographs as spheres with multiply idented irregular surfaces, while those fixed at pH 5.5, AS WELL AS CONTROL CHYLOMICRONS FIXED AT BOTH PHs, appeared as spheres with smooth surfaces. Sections of OSO4-fixed specimens, viewed with the transmission electron microscope, showed that the core of lipolyzed chylomicrons fixed at pH 7.4 contained numerous circular electron-lucent areas at the periphery, thus accounting for the indented surfaces observed above, while the core surfaces of the other specimens were circular and smooth. These findings confirm an earlier report that aqueous spaces form in chylomicrons during lipolysis when albumin in the medium is limited, and that the aqueous spaces disappear when specimens are prepared at pH 5.5 for microscopy. Thin sections of specimens that had been prepared for scanning electron microscopy showed that the gold-palladium coating was desposited directly on the indented surface of the lipid core of lipolyzed chylomicrons fixed at pH 7.4. It is concluded that vacuum dehydration during specimen preparation ruptures the outer wall of the aqueous spaces in lipolyzed chylomicrons and thereby exposes the interior of the spaces to gold-palladium coating and viewing with the scanning electron microscope.
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PMID:Scanning electron microscopic study of chylomicrons incubated with lipoprotein lipase. 0 92

Hormone-sensitive lipase and cholesterol ester hydrolase of chicken adipose tissue were markedly activated by adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase (on the average, 235 to 275%; occasionally as much as 1000%). Diglyceride and monoglyceride hydrolases were also activated, but to a lesser extent (60 to 87%). The activation of all four hydrolases was inhibited by protein kinase inhibitor and reversed by the addition of exogenous protein kinase. Following activation by cAMP-dependent protein kinase, all four hydrolases were deactivated in a Mg2+-dependent reaction and then reactivated to or near initial levels on incubation with cAMP and Mg2+-ATP. The reversible deactivation is assumed to reflect activity of one or more protein phosphatases. The maximum activation obtainable for the four hydrolases decreased when the tissue had been previously exposed to glucagon, indicating that the glucagon-induced activation was probably similar to or identical with the activation demonstrated in cell-free preparations. The pH optima for the four hydrolase activities were similar (7.13 to 7.38). Although the absolute activities and relative degrees of kinase activation differed according to the particular emulsified substrates used, the results do not rule out the possibility that all four hydrolase activities are referable to a single hormone-sensitive hydrolase. Hormone-sensitive acyl hydrolases were separated from lipoprotein lipase by heparin-Sepharose affinity chromatography. Lipoprotein lipase was active against triolein, diolein, and monoolein, but not cholesterol oleate. Incubation of lipoprotein lipase with exogenous protein kinase, cAMP, and Mg2+ATP had no effect on any of the three hydrolase activities. Lipoprotein lipase was further purified to homogeneity and used to prepare antiserum in rabbits. The immunoglobin G fraction from these antisera completely inhibited lipoprotein lipase eluted from heparin-Sepharose columns. However, the hormone-sensitive hydrolase activities (not retained on heparin-Sepharose affinity chromatography) were not inhibited by anti-lipoprotein lipase immunoglobin G, and anti-lopoprotein lipase immunoglobin G did not affect the activation process in crude fractions. Thus, hormone-sensitive lipase and lipoprotein lipase, functionally distinct enzymes, have been physically resolved and immunochemically distinguished. Apparently lipoprotein lipase activity is not regulated, at least directly, by cAMP-dependent protein kinase.
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PMID:Triglyceride, diglyceride, monoglyceride, and cholesterol ester hydrolases in chicken adipose tissue activated by adenosine 3':5'-Monophosphate-dependent protein kinase. Chromatographic resolution and immunochemical differentiation from lipoprotein lipase. 0 45

Lipoprotein lipase activity has been found in the milks from severals species where it is assumed to result from leakage from the mammary gland into milk. The function of the enzyme in the gland is apparently to assist in the transfer of blood lipoprotein triacylglycerol fatty acids into milk triacylglycerols. Bovine skim milk is one of the richest sources of lipoprotein lipase and this enzyme has been purified extensively (7000 fold) by affinity chromatography. The lipase has a molecular weight of about 62000, is inhibited by protamine sulfate, 1.0 M sodium chloride, apolipoprotein C-I (apolipoprotein-serine), and apolipoprotein C-III (apolipoprotein-alanine). The enzyme is activated by apolipoprotein C-II (apolipoprotein-glutamic acid), serum, and by heparin to which it also binds. The lipase is highly specific for the primary esters of acylglycerols and exhibits a slight stereospecificity for the sn-1 ester in preference to the sn-3-ester. Bovine milk also has separate activity toward 1-monoacylglycerols. Human milk contains a serum stimulated lipoprotein lipase with many of the characteristics of the enzyme in bovine milk, as well as an enzyme stimulated by bile salts which resembles the sterol ester hydrolase of rat pancreatic juice. The assay, function, purification, characteristics, and substrate specificities of these enzyme are discussed.
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PMID:Milk lipoprotein lipases: a review. 0 79

Human heart lipoprotein lipase was purified by affinity chromatography on heparin-Sepharose 4B. When crude extracts of heart acetone powder were applied to columsn, about 40% of total lipase activity was bound to the gel and then eluted with 1.5 M NaCl. At this stage the eluted enzyme was purified 1900-fold. Disc gel electrophoresis yielded a single protein band corresponding with lipolytic activity. Minimum molecular weight of the protein was 60,000 as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The purified enzyme was highly unstable; however, its activity could be partially stabilized at --20C by bovine serum albumin, glycerol, or ethylene glycol. The activity of the purified enzyme (i) had a pH optimum between 7.8 and 8.0; (ii) required serum for full enzymatic activity; apoC-II could be substituted for serum; (iii) was inhibited by by apoC-I in the presence of activated substrate; (iv) was markedly inhibited by NaCl; and (v) was stimulated by heparin.
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PMID:Purification and characterization of lipoprotein lipase from human heart. 0 61

A method is described for the assay of lipoprotein lipase, using a stable, radioactive substrate emulsion. Fatty acid-labeled trioleoylglycerol was emulsified by homogenization in glycerol with lecithin as detergent. This anhydrous emulsion was stable for at least six weeks. Substrate solutions for enzyme assay were prepared by diluting the emulsion with buffer containing serum and albumin. The fatty acid produced on hydrolysis was isolated in a one-step liquid-liquid partition system. Incubations with extracts of acetone powders from adipose tissue displayed characteristics of lipoprotein lipase activity, i.e., serum dependence and inhibition by NaCl and protamine. The method is rapid (less than 1 hour), sensitive and reproducible, and suitable for routine use.
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PMID:A stable, radioactive substrate emulsion for assay of lipoprotein lipase. 0 64

A triglyceride lipase was extracted from defatted pig adipose tissue powder with dilute ammonia and purified about 230-fold by a combination of ammonium sulfate fractionation, heparin-Sepharose 4B, DEAE-cellulose, and Sephadex G-150 column chromatographies and isoelectrofocusing electrophoresis. The enzyme was distinguishable in physical and kinetic properties from the two previously defined lipases in adipose tissue, lipoprotein lipase, and hormone-sensitive lipase. The purified enzyme was fully active in the absence of serum lipoprotein and was not stimulated by adenosine 3':5'-monophosphate-dependent protein kinase. In marked contrast to the already defined lipases, the enzyme was strongly inhibited by serum albumin. The enzyme had a molecular weigt of about 43,000, a pI of 5.2, and pH optimum of 7.0. The enzyme hydrolyzed triolein to oleic acid and glycerol, and did not exhibit esterase activity. The apparent Km for triolein was 0.05 mM. Physiological roles of this new species of lipase remained to be explored.
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PMID:Partial purification and characterization of a triglyceride lipase from pig adipose tissue. 1 Feb 95


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