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

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 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

A triacylglycerol lipase in a mitochondrial fraction isolated from yeast (Saccharomyces cerevisiae) has been characterized and the hydrolysis studied kinetically using an insoluble artificial triacylglycerol suspension. 1. The triacylglycerol was hydrolyzed almost completely to fatty acids and glycerol. The lipase activity was inhibited by potassium fluoride and the sodium salts of -chloride, -glycocholate and -pyrophosphate as well as by protamine sulfate but at concentrations much too high to indicate that the lipase is a non specific esterase or a lipoprotein lipase. Also parachloromercuribenzoate inhibited the lipase activity. Inhibitory effect of fatty acid was observed at concentrations above 1mM. This inhibition may provide a regulatory mechanism of the lipase in vivo. 2. On the day of isolation the lipase activity of intact mitochondria at pH 7.5 and 30 degrees C was 400 nmol free fatty acid -h-1 - mg-1 at a triacylglycerol concentration of 9.0 mM. Sonication of the mitochondria increased the activity 2-3 fold. Freezing of the mitochondria also activated the lipase and this activation was dependent upon the freezing method, the concentration of mitochondrial protein and the presence of bovine serum albumin. 3. The particulate nature of the assay system was illustrated by the observation that the apparent Km value of the lipase increased with the concentration of mitochondrial protein. For each protein concentration the lipase had two apparent Km values when the activity was assayed with intact mitochondria, but only one when assayed with submitochondrial particles. At the same protein concentration the Km value for the latter was identical with the "low affinity" Km for the lipase in intact mitochondria.
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PMID:Properties of triacylglycerol lipase in a mitochondrial fraction from baker's yeast (Saccharomyces cerevisiae). 1 Sep 87

A new assay procedure for triglyceride lipase [EC 3.1.1.3] was developed in which radioactive triolein was dissolved in ethanol and directly added to the reaction mixture in the absence of serum and albumin. In the rat adipose tissue there appeared to be a triglyceride lipase measurable with this assay in addition to the two previously defined lipases, lipoprotein lipase [EC 3.1.1.34] and hormone-sensitive lipase. The enzyme was active in the absence of serum and was strongly inhibited by albumin. The molecular weight was estimated to be about 42,000. Adenosine 3',5'-monophosphate-dependent protein kinase [EC 2.7.1.27] was unable to activate the enzyme. The three species of lipases mentioned above behaved differently upon chromatography on a Sepharose 4B column, and were distinguishable from each other in their physical and kinetic properties. The physiological roles of the new species of lipase remain to be explored.
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PMID:Studies on triglyceride lipases from rat adipose tissue. 1 45

A preparation of cerebral microvessels was used to demonstrate the presence of lipoprotein lipase and acid lipase activity in the microvasculature of rabbit brain. Microvessels, consisting predominantly of capillaries, small arterioles, and venules, were islated from rabbit brain. Homogenates were assayed for lipolytic activity using a glycerol-stabilized trioleoylglycerol-phospholipid emulsion as substrate. Lipoprotein lipase activity was characterized with this substrate by previously established criteria including an alkaline pH optimum, increased activity in the presence of heparin and heat-inactivated plasma, and reduced activity in the presence of NaCl and protamine sulfate. A different substrate, containing trioleoylglycerol incorporated into phospholipid vesicles, was used to reveal acid lipase activity that was not affected by heparin, plasma, NaCl, or protamine sulfate. Lipoprotein lipase did not show activity with the vesicle preparation as substrate. Intact microvessels, when incubated in the presence of heparin, release lipoprotein lipase into the incubation solution. In contrast, release of acid lipase activity from intact microvessels was not dependent on heparin. The data show the presence of both lipoprotein lipase and acid lipase in brain microvessels and suggest that lipoproteins are metabolized within the cerebral vasculature.
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PMID:Lipoprotein lipase and acid lipase activity in rabbit brain microvessels. 3 80

A rabbit antiserum prepared against the serum-stimulated lipase (lipoprotein lipase) from bovine milk crossreacted with serum-stimulated lipases from human milk and from human postheparin plasma, but not with bile salt-stimulated lipase from human milk or with salt-resistant lipase from human postheparin plasma. Thus, the serum-stimulated lipase in bovine milk has immunological determinants in common with the serum-stimulated lipases in human milk and in human postheparin plasma. The time-courses for the appearance of serum-stimulated lipase and salt-resistant lipase activities in human plasma after heparin injection were different. The two activities were separated by heparin-Sepharose chromatography. After treatment of postheparin plasma with the antiserum only the salt-resistant lipase activity could be eluted from the column. Thus, these two enzyme activities in postheparin plasma reside in two different enzyme molecules.
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PMID:Serum-stimulated lipases (lipoprotein lipases). Immunological crossreaction between the bovine and the human enzymes. 4 50

Some physiologic aspects of the mobilization and fate of free fatty acids are reviewed. The molecular mechanism of the activation of hormone-sensitive lipase in adipose tissue is then discussed. Recent evidence established that hormone-sensitive lipase, concerned with fat mobilization, is both functionally and immunochemically distinct from lipoprotein lipase, concerned with uptake of plasma triglycerides. Lipoprotein lipase activity is not altered by cyclic AMP-dependent protein kinase. The latter enzyme enhances not only triglyceride hydrolase but also monoglyceride, diglyceride and cholesterol ester hydrolase activities in chicken adipose tissue. Finally, it is shown that the activation of all four acyl hydrolases is reversible, the deactivation being magnesium-dependent. Protein phosphatase fractions from heart and liver active against phosphorylase a can reversibly deactivate adipose tissue hormone-sensitive lipase, implying a low degree of substrate specificity for lipase phosphatase.
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PMID:Hormone-sensitive lipase of adipose tissue. 6 71


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