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)

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

Activatable cholesterol esterase and triacylglycerol lipase of rat adrenal were 58-69% recovered in the 100 000 X g supernatant fraction. Activatable triacylglycerol lipase activity was differentiated from the activity of acid lipase and lipoprotein lipase also found in this fraction. Cholesterol esterase was activated 39.7 +/- 13.6% (S.D.) and triacylglycerol lipase 11.9 +/- 2.9% in a reaction dependent on ATP, cyclic AMP, and protein kinase. The two activities were shown by differential inhibition by an organophosphate, and by partial separation on salting out, to be largely due to separate enzymes. The two enzymes bound tightly to substrate emulsions with quantitatively similar distribution between competing emulsions, suggesting concerted binding. Coinciding gel filtration patterns reinforced, The hypothesis of a lipase complex. Cholesterol esterase comprised a major component of higher apparent Km for substrate and molecular weight 3-10(5)-6-10(5) by gel filtration and a minor component of lower apparent Km and heterogeneous molecular weight above 1 million, which was found mostly in complex and lipid.
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PMID:Activatable cholesterol esterase and triacylglycerol lipase activities of rat adrenal and their relationship. 6 45

Metabolism of ruminant adipocytes involves the synthesis and mobilization of lipids. Rates of lipid synthesis from the uptake of preformed fatty acids (via lipoprotein lipase) and de novo synthesis of fatty acids are related to the energy balance. Acetate is the major carbon source for fatty acid synthesis with NADPH originating from the pentose cycle and the isocitrate cycle. Ruminant adipose tissue lacks the ability to utilize for lipogenesis those substrates that generate mitochondrial acetyl CoA because of an absence of ATP citrate-lyase and NADP-malate dehydrogenase. Lipid mobilization in ruminant adipocytes is apparently regulated via cAMP levels and a summary of the compounds investigated for lipolytic responses is presented. The control of lipid synthesis and mobilization is interrelated in ruminant adipose tissue. The coordinated manner in which these two functions are regulated is examined with regard to adipocyte responses to insulin and epinephrine. In both lipid synthesis and lipid mobilization, ruminant adipocytes are uniquely different from nonruminant adipose tissue. The physiological significance and possible basis for these species differences in adipose metabolism are discussed.
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PMID:Intermediary metabolism of adipose tissue. 18 55

A tri-, di-, and monoacylglycerol-hydrolyzing enzyme from rat adipose tissue has been detergent-solubilized and separated from monoacylglycerol lipase (H. Tornqvist and P. Belfrage, 1976, J. Biol. Chem. 251, 813-819) and lipoprotein lipase by use of ion-exchange chromatography, broad and narrow pH range electrofocusing and gel chromatography. The final preparation contained several different proteins. One of these, with an apparent minimum molecular weight of 86,000 by SDS-gel electrophoresis, was identified as the enzyme protein of hormone-sensitive lipase: a) the enzyme activity was reproducibly stimulated 50-100% by incubation with cyclic AMP-dependent protein kinase, cyclic AMP and ATP-Mg2+; b) the relative intensity of the Mw 86,000 protein band, and only this, closely paralleled the enzyme activity during narrow pH range electrofocusing and during subsequent gel chromatography of the electrofocusing enzyme peak fraction; c) only the Mw 86,000 protein extensively incorporated 32p from [gamma-32P]ATP after incubation with protein kinase and cyclic AMP. The pI of the enzyme was 6.7, it had the same Stokes radius on Sephadex G 200 as IgG and was 50% inactivated by 10 micron HgCl2, 20 micron PCMB, 50 micron DFP, 10 mM NaF and non-ionic detergents above their critical micellar concentration.
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PMID:Identification and some characteristics of the enzyme protein of the hormone-sensitive lipase from rat adipose tissue. 66 58

The effect of exposure of porcine pulmonary artery endothelial cells to hypoxic (0% O2) and normoxic (20% O2) conditions for 24 and 48 h on phospholipid metabolism was studied. Sonicates prepared from endothelial cells that were exposed to 24 h of hypoxia showed significant increases in phospholipase A1 (91%), phospholipase C (75%), and diacylglycerol lipase (57%) activities. Hypoxic exposure of cells for 48 h caused an increase in diacylglycerol lipase activity (54%) only. Hypoxia also caused significant decreases in ATP levels and ATP-dependent arachidonyl coenzyme A (CoA) synthetase activity. Phospholipase A2, lysophosphatidylcholine acyltransferase, and diacylglycerol acyltransferase activities were not influenced by 24 or 48 h of hypoxia. When endothelial cells were prelabeled with [3H]arachidonic acid and then exposed to hypoxia, increased counts were recovered from the free fatty acid fraction of medium and from the cell fatty acid esters, lysophospholipids, diacylglycerols, and triacylglycerols. There was a concomitant decreased recovery of counts from cell phospholipids. These results indicate that hypoxic exposure of endothelial cells altered phospholipid metabolism by activating deacylation pathways and inhibiting reacylation via ATP-dependent arachidonyl CoA synthetase.
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PMID:Effect of hypoxia on phospholipid metabolism in porcine pulmonary artery endothelial cells. 159 Apr 10

Diacylglycerol lipase (glycerol ester hydrolase, EC 3.1.1.3) activities were investigated in subcellular fractions from neonatal and adult rat liver in order to determine whether one or more different lipases might provide the substrate for the developmentally expressed, activity monoacylglycerol acyltransferase. The assay for diacylglycerol lipase examined the hydrolysis of sn-1-stearoyl,2- [14C]oleoylglycerol to labeled monoacylglycerol and fatty acid. Highest specific activities were found in lysosomes (pH 4.8) and cytosol and microsomes (pH 8). The specific activity from plasma membrane from adult liver was 5.8-fold higher than the corresponding activity in the neonate. In other fractions, however, no developmental differences were observed in activity or distribution. In both lysosomes and cytosol, 75 to 90% of the labeled product was monoacylglycerol, suggesting that these fractions contained relatively little monoacylglycerol lipase activity. In contrast, 80% of the labeled product from microsomes was fatty acid, suggesting the presence of monoacylglycerol lipase in this fraction. Analysis of the reaction products strongly suggested that the lysosomal and cytosolic diacylglycerol lipase activities hydrolyzed the acyl-group at the sn-1 position. The effects of serum and NaCl on diacylglycerol lipase from each of the subcellular fractions differed from those effects routinely observed on lipoprotein lipase and hepatic lipase, suggesting that the hepatic diacylglycerol lipase activities were not second functions of these triacylglycerol lipases. Cytosolic diacylglycerol lipase activity from neonatal liver and adult liver was characterized. The apparent Km for 1-stearoyl,2-oleoylglycerol was 115 microM. There was no preference for a diacylglycerol with arachidonate in the sn-2 position. Bovine serum albumin stimulated the activity, whereas dithiothreitol, N-ethylmaleimide, and ATP inhibited the activity. Both sn-1(3)- and 2-monooleylglycerol ethers stimulated cytosolic diacylglycerol lipase activity 2-3-fold. The corresponding amide analogs stimulated 28 to 85%, monooleoylglycerol itself had little effect, and 1-alkyl- or 1-acyl-lysophosphatidylcholine inhibited the activity. These data provide the first characterization of hepatic subcellular lipase activities from neonatal and adult rat liver and suggest that independent diacylglycerol and monoacylglycerol lipase activities are present in microsomal membranes and that the microsomal and cytosolic diacylglycerol lipase activities may describe an ambipathic enzyme. The data also suggest possible cellular regulation by monoalkylglycerols.
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PMID:Diacylglycerol metabolism in neonatal rat liver: characterization of cytosolic diacylglycerol lipase activity and its activation by monoalkylglycerols. 163 59

Cholesterol ester hydrolase activity has been studied in mammary glands of rats. Subcellular fractionation of the glands obtained in mid-lactation indicated that around 80% of the recovered activity was associated with particulate fractions. Two distinct cholesterol ester hydrolase activities were identified, one with an optimum pH of 7.5-9.0 and the second (approximately 5% of the total activity) with a more acidic pH optimum. Although the neutral cholesterol ester hydrolase had some properties in common with the lipoprotein lipase in mammary tissue, it was shown to be a separate entity by several criteria. Its activity could be increased following treatment with Mg-ATP and cAMP-dependent protein kinase, suggesting identity with the hormone sensitive lipase of adipose tissue. The cholesterol ester hydrolase activity in mammary glands just after parturition was greater than in glands obtained either from late-pregnant or midlactating animals. The subcellular distribution of the neutral cholesterol ester hydrolase suggested that it may have a different function to the neutral cholesterol ester hydrolase of adrenals and other tissues. Nevertheless the fact that the activity of the enzyme can be modulated by cAMP-dependent protein kinase suggests the possibility that hormonal control of this enzyme may be involved in the regulation of cholesterol metabolism in the mammary gland.
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PMID:Cholesterol ester hydrolase activity in mammary tissue of the lactating rat. 164 25

In pancreatic islets the bulk of phosphoinositide-specific phospholipase C (PI-PLC) activity was cytosolic. The soluble enzyme was activated by submicromolar concentrations of Ca2+, independent of calmodulin. It was unaffected by glucose and a series of glycolytic intermediates, including glyceraldehyde 3-phosphate. These observations lend support to the hypothesis that glucose-stimulated inositol triphosphate production in islets may be secondary to and provoked by glucose-mediated Ca2+ influx. All four pyridine nucleotides stimulated PI-PLC. Phosphatidylinositol hydrolysis was also stimulated by dioleine and arachidonic acid, and by the polyamines, putrescine and spermine. Phosphatidylinositol hydrolysis was inhibited by chlorpromazine, tetracaine, ATP, 5'-AMP, inorganic pyrophosphate and by phosphatidylinositol 4,5-bisphosphate, phosphatidylcholine and phosphatidylserine--but not affected by phosphatidylethanolamine. The cyclic nucleotides, cAMP and cGMP had no effect on the enzyme, and GTP-gamma-S did not activate the enzyme event at very low Ca2+ concentrations. The diglyceride lipase inhibitor, RHC 80267, and the cyclooxygenase inhibitor, indomethacin, had no effect on PI-PLC activity.
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PMID:Characteristics of phosphoinositide-specific phospholipase C activity from mouse pancreatic islets. 166 77

Elevations in the mass of ether-linked diglycerides (i.e. 1-O-alk-1'-enyl-2-acyl-sn-glycerol (AAG) and 1-O-alkyl-2-acyl-sn-glycerol (Alkyl AG)) during cellular activation are prolonged in comparison to their 1,2-diacyl-sn-glycerol (DAG) counterparts. Since the metabolic removal of DAG is determined, in large part, by the rate of its phosphorylation by diglyceride kinase, we quantified differences in the activity of diglyceride kinase utilizing individual subclasses of diradyl glycerols as substrate. Rabbit brain microsomal diglyceride kinase activity was over 30-fold greater utilizing DAG as substrate (25.8 nmol.mg-1.min-1) in comparison to AAG (0.8 nmol.mg-1.min-1). No alterations in the affinity of microsomal diglyceride kinase for ATP were present (Km approximately 0.5 mM) utilizing each diradyl glycerol subclass. Similar subclass specificities for diglyceride kinase (i.e. DAG greater than Alkyl AG much greater than AAG) were present in brain and liver cytosol as well as in liver microsomes utilizing multiple assay conditions. In sharp contrast, Escherichia coli diglyceride kinase phosphorylated DAG, Alkyl AG, or AAG diradyl glycerol molecular subclasses at identical rates. Furthermore, although DAG was rapidly hydrolyzed by diglyceride lipase, catabolism of AAG or Alkyl AG by plasmalogenase, alkyl ether hydrolase, or diglyceride/monoglyceride lipase was undetectable. Collectively, these results demonstrate the importance of the differential catabolism of each diradyl glycerol molecular subclass as a primary determinant of their biologic half-lives. Since individual subclasses of diglycerides have distinct physical properties and physiologic functions, these results underscore the importance of lipid subclass specific metabolism in tailoring individual cellular responses during activation.
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PMID:Differential metabolism of diradyl glycerol molecular subclasses and molecular species by rabbit brain diglyceride kinase. 216 56

G protein regulation of human platelet membrane phospholipase A2 activity was investigated at pH 8.0 and 9.0 by studying the effects of the nonhydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), and of F-/Al3+ ions on arachidonic acid (AA) release. The membrane acted as the source of the enzyme, the substrate, and the G protein. At pH 8.0, 10 and 100 microM GTP gamma S stimulated AA mobilization at least 6-fold. Optimum AA release conditions required 1 mM Ca2+ and 5 mM Mg2+. Nonspecific nucleotide effect was excluded since similar stimulatory effects on AA release were not observed by ATP, GTP, ADP, and NADP. Although at pH 9.0 the GTP gamma S-stimulated AA release was greater than at pH 8.0, it constituted only 26% of the total. At both pH values the effect of F- (10 mM) in the presence of Al3+ (2 microM) was similar to that of GTP gamma S. The G protein inhibitor, guanosine 5'-O-(2-thiodiphosphate), inhibited the GTP gamma S-stimulated AA release by about 80% at pH 8.0 and by 100% at pH 9.0. To determine a possible contribution to AA mobilization by the phospholipase C and diacylglycerol lipase pathway, the effects of neomycin, a phospholipase C inhibitor, were investigated. 100 microM neomycin did not inhibit the GTP gamma S-stimulated AA release at pH 8.0 and only slightly so (17%) at pH 9.0. At pH 8.0 in the presence of Ca2+ the released fatty acids consisted mainly of arachidonic and docosahexaenoic acids (80 and 8%, respectively). GTP gamma S had no effect on the fatty acid profile but only on their quantity. These results provide evidence of G protein regulation of phospholipase A2 activity in isolated platelet membranes.
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PMID:Evidence of GTP-binding protein regulation of phospholipase A2 activity in isolated human platelet membranes. 251 18


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