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)

Vascular endothelium is the dynamic interface in transport of lipid from blood to myocytes in heart and arteries. The luminal surface of endothelium is the site of action of lipoprotein lipase on chylomicrons and VLDL and the site of uptake of fatty acids from albumin. Fatty acids and monoacylglycerols are transported from the lumen in an interfacial continuum of endothelial and myocyte membranes. Lipoprotein lipase is transferred from myocytes to the vascular lumen, and is anchored there, by proteoheparan sulfate in cell membranes. Insulin, needed for synthesis of lipoprotein lipase and esterification of fatty acids, is captured from the blood stream and delivered to myocytes by endothelial insulin receptors. Fatty acids, monoacylglycerols, lipoprotein lipase and insulin are transported along the same route, but by different mechanisms. The route involves the plasma membrane of endothelium and myocytes, the membrane lining transendothelial channels, and intercellular contacts.
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PMID:Endothelium, the dynamic interface in cardiac lipid transport. 148 Jan 47

Lipoprotein lipase (LPL), hepatic lipase, and pancreatic lipase show high sequence homology to one another. The crystal structure of pancreatic lipase suggests that it contains a trypsin-like Asp-His-Ser catalytic triad at the active center, which is shielded by a disulfide bridge-bounded surface loop that must be repositioned before the substrate can gain access to the catalytic residues. By sequence alignment, the homologous catalytic triad in LPL corresponds to Asp156-His241-Ser132, absolutely conserved residues, and the homologous surface loop to residues 217-238, a poorly conserved region. To verify these assignments, we expressed in vitro wild-type LPL and mutant LPLs having single amino acid mutations involving residue Asp156 (to His, Ser, Asn, Ala, Glu, or Gly), His241 (to Asn, Ala, Arg, Gln, or Trp), or Ser132 (to Gly, Ala, Thu, or Asp) individually. All 15 mutant LPLs were totally devoid of enzyme activity, while wild-type LPL and other mutant LPLs containing substitutions in other positions were fully active. We further replaced the 22-residue LPL loop which shields the catalytic center either partially (replacing 6 of 22 residues) or completely with the corresponding hepatic lipase loop. The partial loop-replacement chimeric LPL was found to be fully active, and the complete loop-replacement mutant had approximately 60% activity, although the primary sequence of the hepatic lipase loop is quite different. In contrast, replacement with the pancreatic lipase loop completely inactivated the enzyme. Our results are consistent with Asp156-His241-Ser132 being the catalytic triad in lipoprotein lipase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Functional topology of a surface loop shielding the catalytic center in lipoprotein lipase. 151 Sep 14

Lipoprotein lipase and hepatic lipase are members of the lipase gene family sharing a high degree of homology in their amino acid sequences and genomic organization. We have recently shown that isolated hepatocytes from neonatal rats express both enzyme activities. We show here that both enzymes are, however, differentially regulated. Our main findings are: (i) fasting induced an increase of the lipoprotein lipase activity but a decrease of the hepatic lipase activity in whole liver, being in both cases the vascular (heparin-releasable) compartment responsible for these variations. (ii) In isolated hepatocytes, secretion of lipoprotein lipase activity was increased by adrenaline, dexamethasone and glucagon but was not affected by epidermal growth factor, insulin or triiodothyronine. On the contrary, secretion of hepatic lipase activity was decreased by adrenaline but was not affected by other hormones. (iii) The effect of adrenaline on lipoprotein lipase activity appeared to involve beta-adrenergic receptors, but stimulation of both beta- and alpha 1-receptors seemed to be required for the effect of this hormone on hepatic lipase activity. And (iv), increased secretion of lipoprotein lipase activity was only observed after 3 h of incubation with adrenaline and was blocked by cycloheximide. On the contrary, decreased secretion of hepatic lipase activity was already significant after 90 min of incubation and was not blocked by cycloheximide. We suggest that not only synthesis of both enzymes, but also the posttranslational processing, are under separate control in the neonatal rat liver.
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PMID:Lipoprotein lipase and hepatic lipase activities are differentially regulated in isolated hepatocytes from neonatal rats. 156 12

Lipoprotein lipase was expressed in Chinese hamster ovary (CHO) cells transfected with human lipoprotein lipase cDNA. The lipoprotein lipase retained tributyrin, water-soluble substrate, hydrolyzing activity (esterase activity). The catalytic action of this enzyme was studied by monitoring the esterase activity. The esterase activity was enhanced 4.5-fold by the addition of triolein emulsified with Triton X-100. This process was named interfacial activation. Treatment of LPL with trypsin (100 micrograms/ml, 37 degrees C for 10 min) caused the loss of the triolein hydrolyzing activity without that of the esterase activity. The esterase activity of trypsin-treated LPL was not enhanced by the addition of the triolein emulsion. The trypsin-treated LPL retained the ability to bind to very low density lipoproteins (VLDL). These results are consistent with the idea that LPL has a catalytic site and a lipid interface recognition site, and that the enzyme undergoes interfacial activation, in which the concealed catalytic site is revealed after the enzyme binds to the surface. Based on this hypothesis, the results obtained suggest that trypsin nicking may impair the interfacial activation process and cause the loss of the lipase activity.
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PMID:Trypsin treatment may impair the interfacial activation action of lipoprotein lipase. 161 42

1. The effect of TGF-beta and bFGF on lipoprotein lipase activity in chicken adipocyte precursors was investigated. 2. Lipoprotein lipase activity was reduced by up to 80% by incubation with TGF-beta whereas bFGF had no effect. 3. Contrary to that found with the 3T3-L1 preadipocyte cell line it was not necessary for TGF-beta to be present prior to the start of differentiation in order to be effective. 4. Incubation of adipocyte precursors with actinomycin D abolished the effect of TGF-beta suggesting that synthesis of a protein effector is required. 5. These results indicate differences in responsiveness to TGF-beta and bFGF between primary chicken adipocyte precursors and some preadipocyte cell lines.
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PMID:Effects of transforming growth factor beta 1 and basic fibroblast growth factor on lipoprotein lipase activity in primary cultures of chicken (Gallus domesticus) adipocyte precursors. 168 63

Lipoprotein lipase (LPL; EC 3.1.1.34) may promote atherogenesis by producing remnant lipoproteins on the endothelial surface and by acting on lipoproteins in the artery wall. In vitro, smooth muscle cells and macrophages synthesize LPL, but in human carotid lesions only a few smooth muscle cells were reported to contain LPL protein. Endothelial cells do not synthesize LPL in vitro, but in normal arteries intense immunostaining for LPL is present on the endothelium. We used Northern blot analysis, in situ hybridization, and immunocytochemistry of human and rabbit arteries to determine cellular distribution and the site of the synthesis of LPL in atherosclerotic lesions. Northern blot analysis showed that LPL mRNA was detectable in macrophage-derived foam cells isolated from arterial lesions of "ballooned" cholesterol-fed rabbits. In situ hybridization studies of atherosclerotic lesions with an antisense riboprobe showed a strong hybridization signal for LPL mRNA in some, but not all, lesion macrophages, which were mostly located in the subendothelial and edge areas of the lesions. Also, some smooth muscle cells in lesion areas also expressed LPL mRNA. Immunocytochemistry of frozen sections of rabbit lesions with a monoclonal antibody to human milk LPL showed intense staining for LPL protein in macrophage-rich intimal lesions. The results suggest that lesion macrophages and macrophage-derived foam cells express LPL mRNA and protein. Some smooth muscle cells in the lesion areas also synthesize LPL. These data are consistent with an important role for LPL in atherogenesis.
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PMID:Macrophages and smooth muscle cells express lipoprotein lipase in human and rabbit atherosclerotic lesions. 171 46

Elevated values of circulating triglycerides were observed in streptozotocin-hyperglycemic rat while cholesterol concentrations did not differ from controls. Daily oral administration of sodium metavanadate to these diabetic animals normalized blood glucose values without raising the reduced levels of insulin. Concomitant with the normalization of the glycemia, the elevated triglyceride values found in diabetic rats were also corrected. Lipoprotein lipase activity in adipose and cardiac tissues was significantly decreased in the streptozotocin-diabetic animals. Similarly, the hepatic lipase activity was also depressed. After vanadate treatment, lipoprotein lipase as well as hepatic lipase activities were corrected towards normal values. Thus, vanadate treatment of streptozotocin-diabetic animals induces normalization of blood glucose and triglycerides levels, while maintaining low amounts of circulating insulin. It also restores the depressed activities of adipose and cardiac lipoprotein lipase and hepatic lipase.
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PMID:Lipoprotein lipase in experimental diabetic rats: beneficial effect of vanadate treatment. 186 59

The lipolysis of rat chylomicron polyenoic fatty acid esters with bovine milk lipoprotein lipase and human hepatic lipase was examined in vitro. Chylomicrons obtained after feeding fish oil or soy bean oil emulsions were used as substrates. The lipolysis was followed by gas chromatography or by using chylomicrons containing radioactive fatty acids. Lipoprotein lipase hydrolyzed eicosapentaenoic (20:5) and arachidonic acid (20:4) esters at a slower rate than the C14-C18 acid esters. More 20:5 and 20:4 thus accumulated in remaining tri- and diacylglycerols. Eicosatrienoic, docosatrienoic and docosahexanoic acids exhibited an intermediate lipolysis pattern. When added together with lipoprotein lipase, hepatic lipase increased the rate of lipolysis of 20:5 and 20:4 esters of both tri- and diacylglycerols. Addition of NaCl (final concentration 1 M) during the course of lipolysis inhibited lipoprotein lipase as well as the enhancing effect of hepatic lipase on triacylglycerol lipolysis. Hepatic lipase however, hydrolyzed diacylglycerol that had already been formed. Chylomicron 20:4 and 20:5 esters thus exhibit a relative resistance to lipoprotein lipase. It is suggested that the tri- and diacylglycerol species containing these fatty acids may accumulate at the surface of the remnant particles and act as substrate for hepatic lipase during a concerted action of this enzyme and lipoprotein lipase.
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PMID:Hydrolysis of chylomicron polyenoic fatty acid esters with lipoprotein lipase and hepatic lipase. 195 25

Lipoprotein lipase acts at the luminal surface of capillaries to hydrolyze chylomicron triacylglycerol to fatty acids that are transferred across the capillary wall to tissue cells for reesterification into cellular triacylglycerol. The distribution of lipoprotein lipase in capillaries and the origin of the lipase was studies with electron microscopic immunocytochemistry in heart. Fatty acids are ampipathic molecules and can be visualized as myelin figures in sections and freeze fracture replicas of tissue. We used this cytochemical technique to study fatty acid transport between capillaries and parenchymal cells in adipose tissue perfused with chylomicrons and in adipose tissue stimulated with isoproterenol to hydrolyze intracellular triacylglycerol with. Morphological results in mammary gland indicate that incorporation of chylomicron fatty acids into milk triacylglycerol occurs via transport of fatty acids in membranes leaflets to sites of reesterification. Fatty acids would leave the membrane leaflet when they are reesterified into triacylglycerol to locate within the hydrocarbon domain of intracellular lipid droplets to be sexcreted into milk.
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PMID:Lipoprotein lipase and fatty acid transport in heart, adipose tissue and mammary gland: immuno and cytochemistry. 195 35

Lipoprotein lipase is the rate determining enzyme for the removal of triglyceride rich lipoproteins from the blood stream. We examined whether genetic variation at the lipoprotein lipase gene locus is related to the occurrence of premature coronary artery disease. Two restriction fragment length polymorphisms, revealed by the enzymes HindIII and PvuII, demonstrated alleles designated H1 (17.5 kb), H2 (8.7 kb), P1 (7.0 kb), P2 (4.4 kb and 2.5 kb) respectively. These were studied in 70 Caucasian subjects with severe coronary atherosclerosis in comparison with 122 Caucasian healthy controls. The allelic frequencies for cases and controls were respectively: H2 0.770, 0.579 (P less than 0.001); P2 0.575, 0.554 (P NS). The allelic frequencies of the HindIII and BglII polymorphic sites at the hepatic lipase gene locus were also studied in the same groups of subjects. These showed no differences between cases and controls. We conclude that DNA variation at or adjacent to the lipoprotein lipase gene may contain genetic determinants for the occurrence of premature coronary artery disease.
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PMID:Lipoprotein and hepatic lipase gene variants in coronary atherosclerosis. 198 Aug 16


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