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)

Oxidized low-density lipoprotein (Ox-LDL) has been shown to be taken up by the macrophage-scavenger receptor at an enhanced rate in comparison to native LDL, with consequent cellular cholesterol accumulation. In the present study, we analyzed macrophage interaction with very-low-density lipoprotein (VLDL) from normolipidemic subjects (N-VLDL) that was oxidized in the presence of 10 mumol/L copper ions. Oxidized VLDL (Ox-VLDL) contained increased conjugated dienes and malondialdehyde (MDA) equivalents and showed increased electrophoretic mobility. Gradual fragmentation of VLDL apolipoproteins (apo) was noted, with apo B-100 being the first to be fragmented, followed by apo E and apo C. Degradation of Ox-VLDL by mouse peritoneal macrophages (MPM) was increased almost twofold in comparison to N-VLDL. Upon incubation of VLDL with lipoprotein lipase (LPL), the LPL-treated lipoprotein demonstrated up to 50% increased degradation by macrophages in comparison to control N-VLDL. However, the degradation of LPL-treated Ox-VLDL was decreased by up to 20% in comparison to control Ox-VLDL. Similarly, the addition of apo E to VLDL enhanced its cellular degradation by 56%, whereas a 20% reduction in the degradation of apo E-treated Ox-VLDL was demonstrated in comparison to nontreated Ox-VLDL. These results showed that LPL and apo E, two important regulatory substances in cellular metabolism of plasma lipoproteins, increased macrophage degradation of native VLDL, but reduced the degradation of Ox-VLDL. These inhibitory effects on macrophage uptake of Ox-VLDL suggest that apo E and LPL may possess antiatherogenic potential.
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PMID:Apolipoprotein E and lipoprotein lipase reduce macrophage degradation of oxidized very-low-density lipoprotein (VLDL), but increase cellular degradation of native VLDL. 143 89

In the present study, we have characterized the properties of both diglyceride lipase (lipoprotein lipase, EC 3.1.1.24) and monoglyceride lipases (acylglycerol lipase, EC 3.1.1.23) in an attempt to assess the potential roles of these two enzymes in the release of arachidonate in activated human platelets. Diglyceride lipase exhibited maximal activity at pH 3.5, whereas monoglyceride lipase showed optimal activity at pH 7.0. Neither of the lipases were inhibited by EDTA or stimulated by Ca2+, Mg2+ or Mn2+. Both enzymes, however, were strongly inhibited by Hg2+ and Cu2+, indicating the involvement of sulfhydryl groups in catalytic activity. This suggestion was further supported by their sensitivity toward sulfhydryl inhibitors, with monoglyceride lipase being more susceptible to inhibition. Both lipases were found to be inhibited to a different degree by a variety of antiplatelet drugs blocking aggregation and arachidonate release. Kinetic studies indicated that dichotomous metabolism of diacylglycerol to monoacylglycerol and to phosphatidic acid could occur concurrently, since the apparent Km values for diglyceride lipase and for diglyceride kinase were comparable. Further studies showed that the specific activity of monoglyceride lipase was at least 100-fold higher than that of diglyceride lipase, indicating that the rate-limiting step in the release of arachidonate was the reaction catalyzed by diglyceride lipase.
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PMID:Monoglyceride and diglyceride lipases from human platelet microsomes. 314 16

The lymphatic absorption of cholesterol and plasma clearance of chylomicrons were investigated in Cu-deficient rats (CuD) fed 0.5 mg Cu/kg diet, as compared with Cu-adequate control rats (CuA) fed 7.5 mg/kg diet. Cholesterol absorption was measured by the 14C-radioactivity appearing in the mesenteric lymph at hourly intervals for 8 hr after an intraduodenal dose of [14C]cholesterol. The plasma clearance of chylomicrons was measured at 3, 6, and 10 min after an intravenous dose of chylomicrons labeled in vivo with [3H]retinyl ester. Cumulative [14C]cholesterol absorption and total lymphatic output of cholesterol were significantly decreased in CuD at 4 hr and thereafter, with no change in percentage distribution of free and esterified cholesterol. Over an 8-hr period, 7.3% of the dose was absorbed by CuD and 9.2% by CuA. When [3H]chylomicrons, obtained from a CuD or CuA donor rat, were injected into CuD and CuA recipient rats, the label was cleared faster in CuD during the first 3 min. At 6 and 10 min, however, no significant difference in percentage clearance of the dose was observed between the groups. The half-life (t1/2) of [3H]chylomicrons and the total 3H-radioactivity taken up by the liver during the entire 10-min period did not differ between the groups, regardless of the source of chylomicrons. The activities of both endothelial lipoprotein lipase (LPL) and hepatic lipase (HL) in postheparin plasma were markedly lower in CuD. As expressed in micromoles fatty acid released/hr/ml plasma, the activities of LPL in CuD and CuA were 32.6 +/- 1.9 and 45.6 +/- 1.3, respectively. A similar magnitude of difference was also observed in HL activity. The data provide evidence that copper deficiency impairs the intestinal transport of cholesterol and the peripheral lipolysis of chylomicrons. The data, however, strongly suggest that the hepatic uptake of chylomicron remnants via the apo-E-dependent mechanism may not be impaired in Cu deficiency.
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PMID:Effect of copper deficiency on the lymphatic absorption of cholesterol, plasma chylomicron clearance, and postheparin lipase activities. 342 Jan 6

Glycerol oxidase purified from Aspergillus japonicus AT 008 had Mr = 400,000 and contained 1 mol of protoheme IX and 2 g atoms of copper/mol of enzyme protein. The absorption maxima of the oxidized form were found at 557, 530, 420, 280, and 238 nm, and those of the reduced form at 557 and 430 nm. Anaerobic addition of glycerol to the enzyme produced both a shift of the Soret band from 420 to 410 nm and bleaching of the alpha and beta bands at 557 and 530 nm. The ESR spectrum of glycerol oxidase showed three major signals at g = 1.99, g = 2.00, and g = 2.02. The signals at g = 1.99 and g = 2.02 were diminished by the anaerobic addition of glycerol, and the three signals completely disappeared after the addition of either dithionite or diethyldithiocarbamate. Exposure of glycerol oxidase to a borate buffer of pH 10.0 resulted in activation of the enzyme with concomitant enhancement of the ESR signals at g = 1.99 and g = 2.02. Since glycerol oxidase acts predominantly on glycerol, the enzyme can be employed in a specific colorimetric assay for serum triglycerides in combination with lipoprotein lipase.
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PMID:Glycerol oxidase, a novel copper hemoprotein from Aspergillus japonicus. Molecular and catalytic properties of the enzyme and its application to the analysis of serum triglycerides. 632 80

Three patients with Menkes' disease, an inherited disorder of copper transport, were studied to determine whether the copper deficiency was associated with a lipoprotein disorder. Hypocuprinemia was documented in all three cases. Two patients had severe copper and ceruloplasmin deficiencies, whereas the third patient had a less severe deficiency. Hypertriglyceridemia was observed in the first patient, and elevations in triglyceride, cholesterol, apolipoprotein B (ApoB), and apolipoprotein C-III (ApoC-III) occurred predominantly in the very low density lipoprotein fraction (VLDL). This patient had normal lipoprotein lipase activity but mild glucose intolerance. The second patient had a borderline high cholesterol level with normal plasma triglycerides and apolipoproteins, whereas the third patient appeared to have normal total cholesterol but slightly higher triglycerides with elevated plasma apolipoprotein E (ApoE). No striking differences were observed in the chemical composition of all lipoprotein subfractions between patients and controls except that the neutral lipid content of VLDL was higher in patients than in controls. The ApoB was initially normal in molecular weight but degraded faster than the controls during storage. The appearance of the major low density lipoprotein (LDL) fraction of the first two patients was opaque white, in contrast to clear yellow in the third patient and in the age- and diet-matched controls. This abnormal appearance of LDL in these patients was associated with low plasma levels of beta-carotene and ceruloplasmin. These findings suggest that decreased serum copper levels may be associated with lipid and lipoprotein abnormalities and may enhance lipid peroxidation of LDL accounting for the color change.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Studies of lipids, lipoproteins, and apolipoproteins in Menkes' disease. 648 10

Postheparin plasma lipoprotein lipase has been investigated in male sprague-Dawley rats fed a diet deficient in copper. Deficiency was verified by the detection of anemia, hypercholesterolemia and decreased myocardial copper. Three experiments were done; they showed significant decrease in enzyme activity (40-47% reduction) in deficiency. Copper may be required for the formation of the activator complex of the enzyme. Decreased lipoprotein lipase activity may be responsible for the hypertriglyceridemia of copper deficiency, and that may also explain its hypercholesterolemia.
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PMID:Postheparin plasma lipoprotein lipase in copper-deficient rats. 707 23

A lipase from Aspergillus oryzae was purified by ammonium sulfate fractionation, anion exchange chromatography, hydrophobic interaction chromatography, and anion exchange chromatography. The purified enzyme was a monomeric protein with a molecular mass of 41 kDa estimated by SDS-PAGE and 39 kDa by gel filtration. The optimum pH at 30 degrees C and optimum temperature at pH 7.0 were 7.0 and 30 degrees C, respectively. The enzyme was stable over a pH range of 6-9 at 25 degrees C for 18 h, and up to 30 degrees C at pH 7.0 for 3 h. Ag+, Fe3+, Hg2+, Cu2+, and Zn2+ inhibited the enzyme activity severely. The enzyme was a lipase that hydrolyzed monoacylglycerols and diacylglycerols, but did not hydrolyze triacylglycerols. The N-terminal amino acid sequence of the enzyme was highly homologous with that of the mono- and diacylglycerol lipase from Penicillium camembertii U-150.
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PMID:Purification and characterization of a lipase from Aspergillus oryzae. 767 Jan 77

Native and oxidized low density lipoprotein retention within arterial wall endothelial cell matrix (ECM) is an early event in the pathogenesis of atherosclerosis. Previously we showed lipoprotein lipase (LPL) addition to ECM enhanced the retention of apoB-containing lipoproteins. In the present studies we examined whether the oxidation of low density lipoprotein (LDL) increases its retention by LPL-containing ECM. Except where noted, 125I-labeled moderately oxidized LDL (ModOxLDL) was prepared by long term storage of 125I-LDL. Without LPL, 125I-ModOxLDL matrix binding was low and nonsaturable. LPL preanchored to ECM resulted in 125I-ModOxLDL binding that was saturable and 20-fold greater than in the absence of LPL, with an association constant equal to 2.6 nM. Copper-oxidized LDL (Cu-OxLDL) was able to compete with 125I-ModOxLDL, whereas a 60-fold native LDL excess had no effect. Reconstituted apolipoprotein B from Cu-OxLDL also reduced 125I-ModOxLDL to LPL, whereas liposomes derived from the lipid extract of Cu-OxLDL had no effect on binding. These data suggest that the increased binding of oxidized LDL to LPL-ECM may be due to the exposure of novel apoB binding sites and not an oxidized lipid moiety. 125I-ModOxLDL binding was also not affected by either preincubation with a 300-fold molar excess of apoE-poor HDL or an 340-fold molar excess of Cu-Ox-HDL. In contrast, a 4-fold apoE-rich HDL excess (based on protein) totally inhibited 125I-ModOxLDL matrix retention. Positively charged peptides of polyarginine mimicked the effect of apoE-rich HDL in reducing the 125I-ModOxLDL retention; however, polylysine had no effect. We postulate that the oxidation of LDL may be a mechanism that enhances LDL retention by the ECM-bound LPL and that the protective effects of apoE-containing HDL may in part be due to its ability to block the retention of oxidized LDL in vivo.
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PMID:Oxidation of low density lipoproteins greatly enhances their association with lipoprotein lipase anchored to endothelial cell matrix. 857 20

To study the pathogenesis of hyperlipoidemia and atheromatosis and the metabolism of lipoprotein, we have developed a colorimetric method for simultaneously determining the activities of post-heparinplasma lipoprotein lipase (LPL) and hepatic lipase (HL). The intralipid was kept for LPL and HL at 37 degrees C, pH8.3 for 30 min, with 100 microliters post-heparin plasma. The LPL and HL in the post-heparin plasma could hydrolyse the triglyceride in intralipid into glycerine and free fatty acid (FFA). Determining the amount of FFA by copper-reagent method, we could measure the activities of LPL and HL. The kinetics of LPL and HL in post-heparin plasma was observed. K(m) values for LPL and HL were 0.9 mumol/L and 2.4 mumol/L respectively. The C. V. for LPL and HL were 4.5% (n = 4), 2.9% (n = 6) and 6.4% (n = 6), 4.8% (n = 6) respectively.
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PMID:[The colorimetric method for measuring activities of lipoprotein lipase and hepatic lipase in plasma]. 920 34

We have previously shown that very low density lipoproteins (VLDL, Sf 60-400) from subjects with type IV hyperlipoproteinemia (HTG-VLDL) will induce appreciable cholesteryl ester accumulation in cultured macrophages (J774A.1). The present study examined whether copper-mediated oxidative modification of HTG-VLDL and their remnants would further enhance cholesteryl ester accumulation in J774A.1 cells. Incubation with oxidized VLDL-remnants caused the greatest increase in cellular cholesteryl ester concentrations (54-fold) relative to control cells (P = 0.001). HTG-VLDL and VLDL-remnants each induced similar increases in cholesteryl ester levels (32.3- and 35.8-fold, respectively; both P = 0.001), whereas incubation with oxidized HTG-VLDL brought about only a 20.6-fold increase in cholesteryl ester concentrations (P = 0.014). The increase in cellular cholesteryl ester concentrations induced by oxidized VLDL-remnants was significantly higher (P < or = 0.04) than that induced by all other lipoproteins tested including low density lipoprotein (LDL) and oxidized LDL which caused a 6.7- and a 35.1-fold increase (P < or = 0.0002 for both), respectively. Unlike HTG-VLDL and to a lesser extent VLDL-remnants, uptake of oxidized VLDL and oxidized VLDL-remnants did not require catalytically active, cell secreted lipoprotein lipase. Co-incubation with polyinosine, which blocks binding to the type I scavenger receptor, completely inhibited the cholesteryl ester accumulation induced by oxidized HTG-VLDL, oxidized VLDL-remnants and oxidized LDL (P < or = 0.02). We conclude that oxidation of VLDL-remnants significantly enhances macrophage cholesteryl ester accumulation compared to either HTG-VLDL, VLDL-remnants, or oxidized LDL. Uptake of oxidized VLDL and oxidized VLDL-remnants does not require catalytically active lipoprotein lipase, and involves a receptor that can be competed for by polyinosine.
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PMID:Oxidized type IV hypertriglyceridemic VLDL-remnants cause greater macrophage cholesteryl ester accumulation than oxidized LDL. 961 Jul 67


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