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)

1. Intralipid is a suitable substrate for measuring lipoprotein lipase activity in the presence of other triacylglycerol lipases in heart and myocytes. 2. Triacylglycerol lipase activity in heart and myocytes was increased 10-fold in the presence of serum at pH 7.4 and 8.1. The serum-stimulated activity in myocytes was 95% inhibited by saturating concentrations of antiserum to lipoprotein lipase. 3. Both heparin-releasable and non-releasable lipoprotein lipase fractions had similar Km values for Intralipid and a similar pattern of inhibition by high density lipoprotein but different responses to heparin. 4. Isoproterenol did not alter lipoprotein lipase activity in cardiac myocytes.
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PMID:Lipoprotein lipase in heart and myocytes: characteristics with intralipid as substrate. 158 75

Fatty acids, the preferred substrate in normoxic myocardium, are derived from either exogenous or endogenous triacylglycerols. The supply of exogenous fatty acids is dependent of the rate of lipolysis in adipose tissue and of the lipoprotein lipase activity at the coronary vascular endothelium. A large part of the liberated fatty acids is reesterified with glycerol-3-phosphate and converted to triacylglycerols. Endogenous lipolysis and lipogenesis are intracellular compartmentalized multienzyme processes of which individual hormone-sensitive steps have been demonstrated in adipose tissue. The triacylglycerol lipase is the rate-limiting enzyme of lipolysis and glycerol-3-phosphate acyltransferase and possibly phosphatidate phosphohydrolase are the rate-limiting enzymes of lipogenesis. The hormonal regulation of both processes in heart is still a matter of dispute. Triacylglycerol lipase activity in myocardial tissue has two intracellular sources: 1. the endoplasmic reticular and soluble neutral lipase, and 2. the lysosomal acid lipase. Studies in our laboratory have indicated that whereas lipolysis is enhanced during global ischemia and anoxia, overall lipolytic enzyme activities in heart homogenates were not altered. In addition we were unable to demonstrate alterations in tissue triacylglycerol content and glycerol-3-phosphate acyltransferase activity under these conditions. Lipolysis, is subject to feedback inhibition by product fatty acids. Therefore all processes leading to an increased removal of fatty acids from the catalytic site of the lipase will stimulate lipolysis. These studies will be reviewed. In addition, studies from our department have demonstrated the capacity of myocardial lysosomes to take up and degrade added triacylglycerol-particles in vitro. Such a process, stimulated by Ca2+ and stimulated by acidosis, offers another physiological target for hormone actions.
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PMID:Hormones and triacylglycerol metabolism under normoxic and ischemic conditions. 267 63

Studies were conducted to investigate the effect of E. coli endotoxin administration on hepatic triglyceride lipase (H-TGL) activity in rats, since H-TGL activity is known to behave differently from lipoprotein lipase (LPL) activity in various situations. Plasma triglyceride and free fatty acid concentrations were markedly elevated in animals after injection of endotoxin. Cholesterol and phospholipids were also increased significantly. Lipoprotein analysis by ultracentrifugation showed that the most pronounced increase of lipoproteins was in the VLDL and IDL fractions. Triglyceride lipase activities in post-heparin plasma were markedly decreased. A selective assay for H-TGL activity using a specific antibody revealed that this enzyme as well as LPL is significantly decreased (26% of control) in endotoxic animals. Thus, the increase of VLDL and IDL appears to result from the decrease of both of LPL and H-TGL.
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PMID:Lipid metabolism in endotoxic rats: decrease in hepatic triglyceride lipase activity. 354 May 38

Triacylglycerol lipase with maximal activity at pH 5 was present in adult and fetal lung. The activity was inhibited by serum concentrations used to measure lipoprotein lipase and by 0.5 M NaCl. The activity in homogenates from fetal lung was about 40% of the activity in adult lung homogenates. The activity increased to 80% of the adult levels during the first 24-48 h following birth. Acidic triacylglycerol lipase was present in all subcellular fractions from adult lung. However, the major amount of activity appeared to be associated with lysosomes. Fetal lung contained significantly more activity in the cytosolic fraction compared to the adult. The reaction produced free fatty acids (65%), 1,2(2,3)-diacylglycerol (22%) and 2-monoacylglycerol (12%). Minimal amounts of 1,3-diacylglycerol and 1(3)-monoacylglycerol were formed. Diacylglycerol lipase and monoacylglycerol hydrolase activities at pH 5 were independently determined and both were higher than the triacylglycerol lipase activity. The subcellular distribution of diacylglycerol lipase and monoacylglycerol hydrolase differed from that of triacylglycerol lipase. Overall, the results indicated that the lung has considerable intracellular lipase activity and therefore could readily hydrolyze intracellular triacylglycerol to free fatty acids. The reaction also produced significant amounts of 1,2-diacylglycerol which suggests that triacylglycerol could be a direct source of diacylglycerol for phospholipid synthesis.
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PMID:The activity and properties of an acidic triacylglycerol lipase from adult and fetal rat lung. 394 May 35

1. Combined guinea-pig cortex and cerebellum was shown to contain triglyceride lipase, diglyceride lipase and monoglyceride lipase, which were assayed by the release of [1-(14)C]palmitate from [1-(14)C]palmitoylglycerol esters. Triglyceride lipase and diglyceride lipase were found in all particulate fractions. 2. With osmotically ruptured synaptosomes the rates of release of palmitate from glyceryl tripalmitate and glyceryl dipalmitate were 7-25mumol/h per g of protein and 0.18-0.69mmol/h per g of protein respectively. The logarithm of the rate of hydrolysis of glyceryl monopalmitate increased linearly with the logarithm of protein concentration. The pH optima of triglyceride lipase and diglyceride lipase were between 7 and 8. The pH optimum for monoglyceride lipase was approx. 8. 3. Triglyceride lipase and diglyceride lipase of osmotically ruptured synaptosomes were stimulated by noradrenaline, 5-hydroxytryptamine and adrenaline. Triglyceride lipase of isolated synaptic membranes was stimulated by 0.01-1mm-noradrenaline. Aging of membranes at 0 degrees C decreased activity, which could still be stimulated by noradrenaline. Diglyceride lipase of isolated membranes was stimulated by 1mum-1mm-noradrenaline. The activity of triglyceride lipase in isolated synaptic vesicles was diminished by 1mm-5-hydroxytryptamine.
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PMID:Glyceride lipases in nerve endings of guinea-pig brain and their stimulation by noradrenaline, 5-hydroxytryptamine and adrenaline. 472 38

Triglyceride lipase (TGL) activities in the homogenates of the rat heart muscle were studied. TGL activity per mg protein of heart muscle was the highest in heart muscle homogenate utilizing 2.1 M glycine buffer, pH 8.3 among the assays investigated. The effects of NaCl, serum and heparin on TGL activities in heart muscle homogenates indicated the characteristics of lipoprotein lipase (LPL). Twelve-hour fasting increased heart muscle LPL activity, while enzyme activities in 48 hour- and 72 hour-fasted rats were lower than those in fed rats. LPL activities in heart muscle homogenates in streptozotocin (STZ)-induced diabetic rats either 3 days or 4 weeks after STZ injection, were decreased significantly as compared with those of control rats.
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PMID:Lipoprotein lipase activities in heart muscle of streptozotocin-induced diabetic rats. 670 89

Triglyceride lipase activity was determined in particulate and soluble fractions from rat skeletal muscle homogenates. The fractions exhibited an acid (pH 5,0) optimum with an impressive enhancement in the combined P17 /100 fraction. Methylamine inhibited this acid lipase activity. A further lipase was observed with maximal activity at pH 7,0 and only a small enhancement in the combined P17 /100 fraction and inhibition by diethyl p-nitrophenyl-phosphate but not by protamine sulfate. Lipoprotein lipase activity was identified by the following in vitro criteria: Stimulation of activity by serum, maximal activity at alkaline pH (pH 8,5 - 9,0) and inhibition of activity by NaCl and protamine sulfate. There was a definite enhancement of lipoprotein lipase activity in the combined P17 /100 fraction after the lipase activity has been washed out from the capillary bed with heparin.
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PMID:Characterization of triglyceride lipase activities in rat skeletal muscle. 673 19

Triacylglycerol lipase activities in adrenals and testes of rats were measured and the properties of the enzymes were characterized. The enzymes were extracted from acetone-ether dried powder of the tissues and the crude extracts were applied to a heparin-Sepharose affinity column. The enzymes bound to the column were then eluted at different ionic strengths. Two lipases could be detected in rat adrenals: one was inactivated by the antiserum raised against hepatic triacylglycerol lipase and the other had the properties of lipoprotein lipase. In testes, only lipoprotein lipase could be detected. The results are discussed in connection with the possible functions of these two lipases in organs utilizing lipoprotein-cholesterol for steroid hormone synthesis.
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PMID:Triacylglycerol lipases in adrenals and testes of rats. 714 20

Primary cultures of chromaffin cells from bovine adrenal medullae were used as a model to study lipolytic events during stimulus-secretion coupling. It has been shown that chromaffin cells liberate arachidonic acid in addition to their main secretion product, the catecholamines. To understand more about the mechanism of arachidonic acid liberation, chromaffin cells were labeled with radioactive arachidonic acid, stimulated, and then analyzed for changes in lipid composition. After stimulation with 10(-4) M acetylcholine, the radioactivity of triacylglycerols decreased to the same extent that the free arachidonic acid level rose. This finding suggests that in bovine chromaffin cells a stimulation-dependent triacylglycerol lipase (triacylglycerol hydrolase; EC 3.1.1.3) is involved in arachidonic acid liberation. Further work was performed on detection, characterization, and isolation of this enzyme. Triacylglycerol lipase activity was found in whole cell homogenates and in plasma membrane fractions isolated from adrenal medullary tissue. The plasma membrane lipase showed a pH optimum of 4.3. The apparent Michaelis constant was determined as 3.3 x 10(-4) mol/L. Ca2+ did not influence the enzymatic activity. To differentiate the plasma membrane triacylglycerol lipase from the previously described plasma membrane diacylglycerol lipase of chromaffin cells, the influence of RG 80267, a specific diacylglycerol lipase inhibitor, was examined. RG 80267 (50 microM) inhibited the triacylglycerol lipase by only 24%, although diacylglycerol lipase was totally inhibited with only 20 microM RG 80267. The pH optimum of homogenate lipase was broad, lying between 4 and 7. Starting from the soluble fraction of whole cell homogenates, the triacylglycerol lipase was partially purified by ultracentrifugation and size-exclusion chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of a triacylglycerol lipase that liberates arachidonic acid from bovine chromaffin cells during secretion. 841 52