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)

Intimal tissue from human atherosclerotic aortae was collected by the Dermatome procedure. The tissue was extraved with 5 mM Tris.HCl buffer containing 0.3 M NaCl and 1 mM EDTA, pH 7.4. The ammonium sulfate precipitate between 0.4--0.8 saturation obtained from the extract was fractionated on a DEAE-cellulose column and the effluent was monitored for lipoprotein lipase inhibition employing purified bovine milk enzyme. The substrate used was an emulsion of purified olive oil and tritiated triolein. Human serum was the source of activator of the substrate. A peak of inhibitory activity was eluted between 0.15--0.17 M NaCl. The major component in the purified material had properties similar to a glycoprotein (lipolipin) which has previously been purified from porcine aorta and shown to inhibit lipoprotein lipase activity. The partially purified human inhibitor decreased both the basal and the serum-stimulated activity of milk lipoprotein lipase. The inhibition was non-competitive with respect to serum. However, high levels of triglyceride substrate appeared to relieve the inhibitory effect. It is postulated that the inhibitor may be involved in an interaction with the emulsified lipid denying the enzyme access to its substrate.
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PMID:The in vitro inhibition of bovine milk lipoprotein lipase by a glycoprotein preparation from human atherosclerotic intima. 64 49

The influence of heparin administration on the protein binding of lidocaine was investigated in this study. Epidural anesthesia was conducted in 20 patients undergoing vasoconstructive surgery, and the changes of lidocaine concentration and its protein binding ratio after heparin administration were estimated. Protein binding ratio of lidocaine decreased rapidly after the commencement of heparin injection until attaining the minimal rate of 50.3 +/- 8.8%, and it then recovered gradually. There was a distinct negative correlation between the reduction in protein binding ratio of lidocaine and the increase of non-esterified fatty acid (NEFA) based on the activated lipoprotein lipase after heparin administration. This reduction of protein binding ratio after heparin was in safety range so that practically no dangerous adverse reaction was seen in these patients. The detailed mechanism was elucidated in an in vitro study. Normal concentration of NEFA (300 microEq.l-1) increased the protein binding ratio of lidocaine, and high concentration of NEFA (1800 microEq.l-1) decreased the ratio on human serum albumin (HSA). Heparin (1.0 unit.ml-1) itself, however, showed no influence for protein binding ratio onto HSA. Concerning alpha 1-acid glycoprotein (AAG), NEFA did not show any influence on the binding ratio, and heparin decreased it little. Consequently, it can be said that the protein binding ratio of lidocaine was mainly affected by NEFA concentration.
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PMID:[The influence of heparin administration on the plasma protein binding of lidocaine during epidural anesthesia]. 156 May 80

The post-heparin plasma contains two lipolytic enzymes. This review deals with the lesser known, hepatic triglyceride lipase. Like lipoprotein lipase, H-TGL is a glycoprotein and has an optimal pH of 8-9. But it does not require an activator protein and its activity is not inhibited by NaCl or protamine sulfate. Synthesized by the hepatocytes, H-TGL is located at the hepatic vascular endothelium. It catalyses the hydrolysis of a wide variety of lipid substrates including triacylglycerol and phospholipids. The function of the enzyme is still not fully known. H-TGL may function in the clearance of triglyceride rich lipoprotein remnants and in the catabolism of HDL.
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PMID:[Hepatic triglyceride lipase]. 218 32

Newborn combined lipase-deficient (cld) mice have severe hypertriglyceridemia associated with a marked decrease of lipoprotein lipase (LPL) and hepatic lipase (HL) activities. Since the cld mutation and lipase genes reside on separate chromosomes, combined lipase deficiency cannot result from defects occurring within the LPL or HL structural genes. To elucidate the biochemical basis of this trans-acting defect, cld mice were compared to unaffected littermates for changes in lipase mRNA levels, rates of synthesis, and posttranslational processing and secretion. LPL and HL mRNA levels in cld liver and LPL in cld heart were comparable to controls; corresponding lipase synthetic rates were modestly decreased by about 30%. However, these reduced synthetic rates were not lipase-specific, since the rates of apolipoprotein (apo) A-I and apoA-II synthesis in cld liver were similarly decreased. Despite LPL synthetic rates that were 70% of controls, LPL mass in cld postheparin plasma was markedly reduced to only 7% of control values, suggesting that the majority of LPL is not secreted but remains intracellular. Consistent with a lipase secretory defect, neither the LPL nor HL oligomannosyl forms were converted to their respective complex forms in cld tissues, indicating that the lipases had failed to move from the endoplasmic reticulum/cis-Golgi to the medial/trans-Golgi network. In addition, the majority of intracellular LPL was catalytically inactive, since LPL specific activity (units/mg LPL protein) in cld heart, kidney, and brain was reduced 80-97%. In contrast to the severe impairment of lipase posttranslational processing and secretion, cld mouse plasma contained normal levels of another secretory N-linked glycoprotein, adipsin, with its oligosaccharide chains fully processed to the complex form. Thus, the cld mutation appears not to globally disrupt the secretion of all N-linked glycoproteins, but rather selectively impairs LPL and HL at points essential to their normal intracellular transport and secretion.
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PMID:Combined lipase deficiency in the mouse. Evidence of impaired lipase processing and secretion. 221 73

In an attempt to clarify the mechanism of lipid metabolism during pregnancy, alpha 1-acid glycoprotein (alpha 1-AG) was analyzed in normal and diabetic pregnant women. Seventy-two determinations of serum alpha 1-AG levels were performed in 18 diabetic pregnant women and 82 determinations in 82 normal pregnant women in all three trimesters and within 14 days postpartum. Serum alpha 1-AG levels in both normal and diabetic pregnant women decreased throughout pregnancy and rapidly increased postpartum. In all gestational stages, the serum alpha 1-AG levels were lower in diabetic women than in normal women, but the differences were not significant. No significant correlation was obtained between serum alpha 1-AG and hemoglobin A1 (HbA1) in diabetic patients. On the contrary, the serum triglyceride levels increased during pregnancy and decreased postpartum in both groups of subjects. These findings suggest that serum alpha 1-AG plays an important role in the activation of lipoprotein lipase during pregnancy.
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PMID:Quantitative analysis of serum alpha 1-acid glycoprotein levels in normal and diabetic pregnancy. 226 50

The biosynthesis and turnover of lipoprotein lipase (LPL) have been investigated in adipose 3T3-F442A cells labeled with [35S]methionine. Pulse-chase experiments, endo-beta-N-acetylglucosaminidase H treatment, and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis have indicated that LPL is synthesized in the endoplasmic reticulum as a glycoprotein of Mr = 55,500 bearing two N-oligosaccharide side chains of the high mannose-type. This precursor form of LPL is transported within 10 min to the Golgi apparatus, and this event is accompanied by the formation of a mature species of Mr = 58,000. Treatment of the Mr = 58,000 species with glycopeptidase F yielded a Mr = 51,000 protein similar to that observed after treatment of the Mr = 55,500 precursor form or after inhibition of N-glycosylation in tunicamycin-treated cells. The precursor form of LPL of Mr = 55,500 does not accumulate in the cells since, after a labeling period of 2 h, only the Mr = 58,000 species is detected. It is shown that only 20% of the newly synthesized molecules of Mr = 58,000 are constitutively secreted, whereas 80% are degraded, most likely in lysosomes, as indicated by the inhibitory effect of leupeptin upon the degradation process. Under heparin stimulation, quantitative secretion of the mature form of LPL takes place whereas the intracellular degradation is arrested. Heparin is able to mobilize intracellular LPL without changing the rate of LPL export from the endoplasmic reticulum to the cell surface. Sucrose gradient centrifugation of the material from intracellular cisternae shows that the Mr = 55,500 precursor form is present as a monomer (s = 4.1 S), whereas the Mr = 58,000 mature form is present as a homodimer (s = 6.8 S) to which LPL activity is associated. The results are interpreted as LPL being transiently stored under a dimeric form before its degradation. A sorting process of LPL in the Golgi apparatus, followed by its entry either mainly in a regulated pathway or in a constitutive pathway, is proposed.
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PMID:Biosynthesis of lipoprotein lipase in cultured mouse adipocytes. II. Processing, subunit assembly, and intracellular transport. 275 12

Glucidamine, a purified glycoprotein-mucopolysaccharide complex displays dose-dependent lipolytic effect on human adipose tissue in vitro. On adipose tissue lipoprotein lipase activity glucidamine exhibits an heparin-like effect in eluting the enzyme from the tissue stores to the medium of incubation. No activating effects of glucidamine on lipoprotein lipase eluted from human adipose tissue was observed.
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PMID:In vitro effects of glucidamine on adrenergic stimulated lipolysis and on lipoprotein lipase activity in human adipose tissue. 294 97

Bovine brain contains two diacylglycerol lipases. One is localized in purified microsomes and the other is found in the plasma membrane fraction. The microsomal enzyme is markedly stimulated by the non-ionic detergent, Triton X-100, and Ca2+, whereas the plasma membrane diacylglycerol lipase is strongly inhibited by Triton X-100 and Ca2+ has no effect on its enzymic activity. Both enzymes were solubilized using 0.25% Triton X-100. The solubilized enzymes followed Michaelis-Menten kinetics. The apparent Km values for microsomal and plasma membrane enzymes are 30.5 and 12.0 microM respectively. Both lipases are strongly inhibited by RHC 80267, with Ki values for microsomal and plasma membrane diacylglycerol lipases of 70 and 43 microM, respectively. The retention of microsomal diacylglycerol lipase on a concanavalin A-Sepharose column and its elution by methyl alpha-D-mannoside indicates the glycoprotein nature of this enzyme.
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PMID:Characterization and solubilization of membrane bound diacylglycerol lipases from bovine brain. 310 Mar 58

Heparan sulfate proteoglycans were extracted from rat brain microsomal membranes or whole forebrain with deoxycholate and purified from accompanying chondroitin sulfate proteoglycans and membrane glycoproteins by ion-exchange chromatography, affinity chromatography on lipoprotein lipase-Sepharose, and gel filtration. The proteoglycan has a molecular size of approximately 220,000, containing glycosaminoglycan chains of Mr = 14,000-15,000. In [3H]glucosamine-labeled heparan sulfate proteoglycans, approximately 22% of the radioactivity is present in glycoprotein oligosaccharides, consisting predominantly of N-glycosidically linked tri- and tetraantennary complex oligosaccharides (60%, some of which are sulfated) and O-glycosidic oligosaccharides (33%). Small amounts of chondroitin sulfate (4-6% of the total glycosaminoglycans) copurified with the heparan sulfate proteoglycan through a variety of fractionation procedures. Incubation of [35S]sulfate-labeled microsomes with heparin or 2 M NaCl released approximately 21 and 13%, respectively, of the total heparan sulfate, as compared to the 8-9% released by buffered saline or chondroitin sulfate and the 82% which is extracted by 0.2% deoxycholate. It therefore appears that there are at least two distinct types of association of heparan sulfate proteoglycans with brain membranes.
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PMID:Isolation and characterization of the heparan sulfate proteoglycans of brain. Use of affinity chromatography on lipoprotein lipase-agarose. 315 51

Previously we found that alpha 2-acid glycoprotein fraction from urine of patients with the nephrotic syndrome stimulated the lipoprotein lipase reaction in vivo and in vitro. The activator was separated from the alpha 1-acid glycoprotein and identified as a glycosaminoglycan. The studies reported here were undertaken to characterize and quantify the glycosaminoglycans contained in urine of patients with the nephrotic syndrome and to compare these to the glycosaminoglycans in urine of the control subjects. We found that free low molecular weight glycosaminoglycans, heparan sulfate and chondroitin 4-sulfate, are excreted in both patients with the nephrotic syndrome and controls however, patients with the nephrotic syndrome excreted much less of both glycosaminoglycans. The free form of heparan sulfate was found to be the activator which stimulated the lipoprotein lipase reaction in vitro in the presence of apolipoprotein CII. In addition, the urine from patients with the nephrotic syndrome contained a protein-glycosaminoglycan complex which was absent in control urine. Glycosaminoglycans in the complex could be released by papain digestion or by trichloroacetic acid. Our evidence indicates that this glycosaminoglycans fraction is a law charge form of chondroitin sulfate.
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PMID:Characterization of glycosaminoglycans in urine from patients with nephrotic syndrome and control subjects, and their effects on lipoprotein lipase. 645 28


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