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)

A lipoprotein lipase in the bovine arterial wall has been identified and partially characterized. The enzyme has a Km apparent of 1 mM for triolein in a phosphatidylcholine stabilized emulsion. The lipase was stimulated 20- to 30-fold by the addition of heated rat plasma to the assay medium. The activity exhibited a pH optimum at 8.6. Protamine sulfate (1.0 mg/ml) inhibited the activity by 50%, whereas 1.4 M sodium chloride inhibited by 85%. Sodium fluoride, an inhibitor of the hormone-sensitive lipase, had no effect on the activity. Additions of low concentrations of heparin or Ca-2+ to the enzyme caused a slight stimulation of the lipolytic activity. A crude sectioning of the aorta revealed specific activity of lipoprotein lipase to be highest at the endothelial side of the artery.
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PMID:Lipoprotein lipase activity in bovine aorta. 23 75

The lipoprotein lipase and tributyrate hydrolysing activities were found to be similarly distributed in the fractions obtained when whole milk was separated into skim-milk and cream, and when the cream was washed and freed from lipid. These enzyme activities in skim-milks and in extracts of lipid-free cream could not be separated by affinity chromatography on heparin-Sepharose. The enzymes were inactivated to the same degree when incubated at 37 degrees C in the presence of 1-5 M-NaCl, pH 8-5, and both showed marked decrease in stability at 4 degrees C in UV-light caused the same decrease in both lipoprotein lipase and tributyrate hydrolysing activities. An antiserum against a highly purified skim-milk lipoprotein lipase caused total inhibition of the lipoprotein lipase and tributyrate hydrolysing activities in skim-milk and in extracts of lipid-free cream. It is suggested that in bovine milk there is only one major lipase and that it is identical to lipoprotein lipase.
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PMID:Lipases in bovine milk and the relationship between the lipoprotein lipase and tributyrate hydrolysing activities in cream and skim-milk. 23 41

The subcellular distributions of acidic (pH 4.5) and neutral (pH 7.5) longchain triacylglycerol lipases (glycerol ester hydrolase, EC 3.1.1.3) of pig liver have been determined. The distribution of the acidic lipase closely paralleled that of the lysosomal marker enzyme, cathepsin D. Approx. 60% of the neutral lipolytic activity resided in the soluble fraction;the distribution of this activity failed to parallel that of marker enzymes for mitochondria, lysosomes, microsomes, or plasma membranes. A method has been developed for purification of the neutral lipase from the soluble fraction by ultracentrifugation. An approximate 90-fold purification was achieved, with recovery of 16% of the initial activity. The partially purified neutral lipase exhibited a pH optimum between 7.25 and 7.5. It required 30 mM emulsified triolein for optimal activity and ceased to liberate fatty acids after 30 min of incubation. The enzymatic activity was destroyed by heating at 60 degrees C. Neutral lipase was inhibited by sodium deoxycholate, Triton X-100 and iodoacetamide. The activity was not inhibited by sodium taurocholate, EDTA, heparin and diethyl-p-nitrophenyl phosphate. Neutral lipase failed to exhibit activity in assay systems specific for lipoprotein lipase, monoolein hydrolase, tributyrinase, and methyl butyrate esterase and showed little or no capacity to hydrolyze chyle chylomicrons or plasma very low density lipoproteins. It is suggested that the function of neutral lipase may be to supply the liver with fatty acids liberated from endogenously synthesized or stored triacylglycerols.
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PMID:Subcellular fractionation, partial purification and characterization of neutral triacylglycerol lipase from pig liver. 23 42

A new method for the selective measurement of postheparin plasma lipoprotein lipase and hepatic lipase is described and validated. The activity of lipoprotein lipase is determined at 0.1 M NaCl after removal of hepatic lipase by specific antiserum, and the hepatic lipase is assayed in a medium containing 1.0 M NaCl but no additional serum. The optimal conditions for the determination of the two postheparin plasma triglyceride hydrolases were shown to be similar to those described for the purified enzymes. The new assay methods are simple, accurate and highly specific for the two lipase activities. VLDL and LDL do not interfere with the measurement, making the methods suitable for studies of patients with various hyperlipidemias. More than 90% of the total triglyceride hydrolase activity in postheparin plasma is precipitated with antisera raised against purified human postheparin plasma hepatic lipase and bovine milk lipoprotein lipase. The time and dose dependence of the two postheparin plasma lipase responses differ. For optimal activity of both enzymes, plasma taken 15 minutes after intravenous administration of 100 I.U./kg of heparin, should be used. The activity of postheparin plasma lipoprotein lipase and hepatic lipase in 12 young, healthy males is reported.
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PMID:An immunochemical method for the selective measurement of two triglyceride lipases in human postheparin plasma. 24 May 22

We provide evidence that the mechanism for arachidonate release from stimulated human platelets involves two enzymes: a phosphatidylinositol-specific phospholipase C (EC 3.1.4.10) and a diglyceride lipase. After incubation of platelets with thrombin for 15 seconds, 1.2 nmol of 1-stearoyl-2-arachidonoyl diglyceride per 10(9) platelets, was isolated. Arachidonate was released from this substrate by the action of diglyceride lipase located in the particulate fraction of platelets. The enzyme has a pH optimum of 7.0, is stimulated by calcium ions and reduced glutathione, and liberates 31 nmol of fatty acid per min per mg of platelet particulate protein. The diglyceride lipase has sufficient activity to account for the 5-10 nmol of arachidonate released per 10(9) platelets upon thrombin stimulation. That only arachidonate is released upon thrombin stimulation may be explained by the fact that the diglyceride substrate in platelets contains only arachidonate in the 2 position. The lipase activity found in platelet membranes can also hydrolyze the 1-position fatty acid. Stearate is not released when intact platelets are stimulated with thrombin, and the fate of this fatty acid remains to be elucidated.
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PMID:Diglyceride lipase: a pathway for arachidonate release from human platelets. 29 Sep 99

1. The in vitro activities of lipoprotein lipase (LPL) and hormone sensitive lipase (HSL) were examined in adipose tissue preparations from pigs 0-150 days of age. 2. The activities of both LPL and HSL increased 3- to 4-fold between birth and day 2 postpartum, remained at relatively high levels through weaning, and fell sharply in the oldest animals (150 days). 3. The decline in enzyme activities at older ages could partially be attributed to an increase in adipocyte size.
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PMID:Ontogenic development of swine (Sus domesticus) adipose tissue lipases. 31 33

Low doses of heparin were injected into the brachial artery of three volunteers. The lipase activities in the deep vein of the same forearm, draining mainly muscle tissue, and in the artery were monitored over a 10-min period. Lipase activity, rapidly released by heparin in the deep vein, was immunologically similar to lipoprotein lipase (E.C. 3.1.1.3), i.e. (1) it did not react with antiserum against human post-heparin plasma hepatic lipase and (2) it was inhibited by an antiserum against bovine milk lipoprotein lipase, which cross reacts with human post-heparin plasma lipoprotein lipase. The evidence that human muscle contains lipoprotein lipase is discussed.
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PMID:Heparin-induced release of lipase activity in the human forearm: an immunological study. 32 91

The amount of free fatty acid in the mouse mammary gland continuously increased throughout pregnancy and lactation, while the amount of triglyceride which had been stored in the gland rapidly decreased after parturition. Higher lipolytic activity in the gland was observed in pregnancy than in nonpregnant and lactating animals. The optimum pH of the activities before and after parturition were about 6 and 7, respectively, and the activities did not decrease at high ionic strength in contrast to the ion dependent inactivation described in lipoprotein lipase. Incubation of the enzyme extract of the lactating mouse mammary gland at 50 degrees C for 10 min led to a remarkable increase in the lipolytic activity measured at pH 6.0, suggesting the existence of either an inactive form of the lipase whose optimum pH is 6.0 or some heat sensitive inhibitor(s) or inactivator(s) of the enzyme in the lactating mammary gland. The triglyceride stored in the gland in pregnancy will be consumed within the first 3rd days after parturition, and the lipases play an important role in the decomposition of the triglyceride.
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PMID:Changes in fat content and some characteristics of lipolytic activity during pregnancy and lactation in mouse mammary gland. 47 24

The fractional elimination rate of fat emulsions of soybean oil, emulsified with egg yolk phosphatides with 1% addition of cholesterol or various cholesteryl fatty acid esters, was studied in rabbits. The fractional removal rate k2%/min was the same after addition of free cholesterol or esters with fatty acids up to eight carbon esters. The k2 values were twice as high for emulsions with cholesteryl-stearate, three times higher with added cholesteryl-palmitate and four times higher when cholesteryl-linoleate was added. The triglyceride (TG) lipase activity was determined with human or rabbit post-heparin plasma and with purified bovine lipoprotein lipase. All these enzyme sources gave similar results. Addition of saturated cholesteryl esters did not affect the lipase activity, but addition of 1% cholesterol markedly decreased the lipase activity. Furthermore, addition of cholesteryl-linoleate and linolenate reduced post-heparin TG lipase activity.
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PMID:Fat emulsions with added free cholesterol or fatty acid cholesteryl esters. Studies on removal mechanisms in vivo and hydrolysis by lipoprotein lipase in vitro. 56 51

1. Post-heparin lipolytic activity in man has been studied by using a triglyceride substrate emulsion containing different emulsifiers. 2. The lipolytic activity measured was profoundly influenced by the type of emulsifier used in the substrate. Substrate stabilized by synthetic emulsifiers give higher lipolytic activity than Intralipid, which contains egg phospholipids as emulsifiers. This difference was solely explained by higher salt-resistant lipase activities found with emulsions containing synthetic emulsifiers. The salt-inhibited lipase activity, which has properties as a lipoprotein lipase, was not influenced by the type of emulsifier. 3. When used under specified conditions Intralipid seems to be virtually specific for extrahepatic post-heparin lipolytic activity.
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PMID:Lipolytic activities in post-heparin plasma in man measured with different substrate emulsions. 62 May 7


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