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)

Lipoprotein lipase activity has been found in the milks from severals species where it is assumed to result from leakage from the mammary gland into milk. The function of the enzyme in the gland is apparently to assist in the transfer of blood lipoprotein triacylglycerol fatty acids into milk triacylglycerols. Bovine skim milk is one of the richest sources of lipoprotein lipase and this enzyme has been purified extensively (7000 fold) by affinity chromatography. The lipase has a molecular weight of about 62000, is inhibited by protamine sulfate, 1.0 M sodium chloride, apolipoprotein C-I (apolipoprotein-serine), and apolipoprotein C-III (apolipoprotein-alanine). The enzyme is activated by apolipoprotein C-II (apolipoprotein-glutamic acid), serum, and by heparin to which it also binds. The lipase is highly specific for the primary esters of acylglycerols and exhibits a slight stereospecificity for the sn-1 ester in preference to the sn-3-ester. Bovine milk also has separate activity toward 1-monoacylglycerols. Human milk contains a serum stimulated lipoprotein lipase with many of the characteristics of the enzyme in bovine milk, as well as an enzyme stimulated by bile salts which resembles the sterol ester hydrolase of rat pancreatic juice. The assay, function, purification, characteristics, and substrate specificities of these enzyme are discussed.
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PMID:Milk lipoprotein lipases: a review. 0 79

A review of radioimmunoassays for measuring human apolipoprotein B (apo B), the A apolipoproteins of high density lipoprotein (apo A-I and apo A-II) and apolipoprotein C-II (apo C-II) in human plasma and in isolated lipoproteins is presented. The sensitivity, specificity and validity of each of these assays is discussed. In normolipidemic subjects the reported serum apo B concentrations ranged between 0.83 +/- 0.16 and 0.92 +/- 0.21 g per l (m +/- SD). Serum apo B concentrations were highest in Type II subjects (Type IIa homozygotes 3.83 +/- 0.43 g per l; Type IIa heterozygotes 2.37 +/- 0.47 g per l) and were less elevated in patients with Type IV and Type V disorders (1.32 +/- 0.21 g per l and 1.26 +/- 0.30 g per l, respectively). Preliminary data on the relationship between plasma apo B and cholesterol, the distribution of apo B amongst the lipoprotein classes and a comparison of the lipoprotein lipid-apo B ratios in the various hyperlipidemic disorders are summarized. In contrast to apo A-II, the immunoreactivity of apo A-I was not fully exposed in whole sera and in isolated lipoproteins. The different methods used to measure the apo A-I immunoreactivity are discussed. In normolipidemic subjects the serum apo A-I concentration in males and females was 1.13 +/- 0.061 and 1.24 +/- 0.068 g per l (m +/- SD), respectively, while the corresponding serum apo A-II values were 0.35 +/- 0.038 g per l and 0.41 +/- 0.046 g per l. In subjects with Tangier's disease, the serum apo A-I and apo A-II concentrations were less than 1 percent and 5 to 7 percent of that found in controls. The serum apo A-I level was also reduced in two subjects with abetalipoproteinemia (0.38 g per l and 0.30 g per l) and Tye II hyperlipoproteinemia (range 0.54 to 0.86 g per l). In normotriglyceridemic subjects and those with Type IIa hyperlipoproteinemia, the total plasma apo C-II concentrations were 0.0497 +/- 0.0040 g per l and 0.0562 +/- 0.0054 g per l (m +/- SE). Plasma apo C-II levels in Type IIb, Type IV and Type V lipoproteinemic subjects were 0.0899 +/- 0.0046, 0.0854 +/- 0.0069 and 0.1328 +/- 0.0021 g per l, respectively and were significantly higher than in the normotriglyceridemic subjects. An analysis of the relationship between the apo C-II content and the lipoprotein lipase activator properties of VLDL isolated from normo- and hypertriglyceridemic plasma samples is presented.
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PMID:Recent progress in the development of radioimmunoassays for human serum lipoproteins. 20 63

The influence of purified human apolipoprotein C-II on phospholipase A1 and triglyceridase activities of lipoprotein lipase were compared. Lipoprotein lipase was obtained from rat hearts by perfusion with a medium containing heparin and purified on a heparin Sepharose 4-B column. Using phosphatidyl-ethanolamine-coated triglyceride particles as substrate it was found that the phospholipase A1 and triglyceridase activities of lipoprotein lipase similarly depend on the presence of apolipoprotein C-II. Apolipoprotein C-III cannot replace apolipoprotein C-II. However, addition of apolipoprotein C-III in the presence of C-II affects both lipase activities. While strong inhibition of triglyceridase activity was observed under these conditions, phospholipase A1 activity was slightly stimulated. On the basis of these findings a model was constructed for the role of apolipoprotein C-II in lipoprotein lipase action.
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PMID:Triglyceridase and phospholipase A1 activities of rat-heart lipoprotein lipase. Influence of apolipoproteins C-II and C-III. 21 Aug 32

A study of the relatives of a patient with apolipoprotein C-II deficiency showed that the defect is inherited as an autosomal recessive trait. The kindred studied originated from an isolated population in which considerable inbreeding has occurred for 140 years. Seven homozygotes had marked fasting chylomicronemia and triglyceridemia, and lacked detectable apolipoprotein C-II by several assay methods. Five homozygotes had experienced one to many attacks of pancreatitis from as early as six years of age. Obligate heterozygotes had apolipoprotein C-II concentrations about 30 to 50 per cent of normal values and had normal plasma triglyceride concentrations. This metabolic defect should be considered in patients with markedly elevated plasma triglycerides who have apparent lipoprotein lipase deficiency, and usually also have pancreatitis.
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PMID:Inheritance of apolipoprotein C-II deficiency with hypertriglyceridemia and pancreatitis. 21 19

The hydrolytic activity of a lipoprotein lipase from bovine milk against triacylglycerol and phosphatidylcholine of rat plasma very low density lipoprotein was determined and compared to that against phosphatidylcholine of high density lipoprotein. 85--90% of the triacylglycerol in very low density lipoprotein were hydrolyzed to fatty acids and 25--35% of the phosphatidylcholine to lysophosphatidylcholine. High density lipoprotein phosphatidylcholine was only minimally susceptible to the enzyme. Even with high amounts of enzyme and prolonged incubation periods, lysophosphatidylcholine generation did not exceed 2--4% of the original amounts of labeled phosphatidylcholine in the high density lipoprotein. We conclude that phospholipids in high density lipoprotein are not substrates for the phospholipase activity of this lipoprotein lipase. These observations suggest that factors other than the presence of apolipoprotein C-II and of glycerophosphatides are of importance for the activity of lipoprotein lipases.
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PMID:Comparison of the phospholipase activity of bovine milk lipoprotein lipase against rat plasma very low density and high density lipoprotein. 21 96

A new kindred with asymptomatic hypobetalipoproteinemia is reported. The proband, age 67, differs from previously described cases in several respects: (a) unusually low levels of low density lipoprotein (LDL) cholesterol (4-8 mg/dl); (b) normal triglyceride levels; (c) low levels of high density lipoprotein; (d) mild fat malabsorption; and (e) a defect in chylomicron clearance. On a high-carbohydrate diet his plasma triglyceride levels, instead of rising, actually fell. Turnover of triglycerides in very low density lipoproteins (VLDL) was low (2.8 mg/kg per h). Fractional catabolic rate of LDL protein was just above the normal range (0.655/d) but net turnover was <10% of normal (0.65 mg/kg per d). The half-life of his chylomicrons was 29 min, five times the normal value. Postheparin lipoprotein lipase activity was normal and apolipoprotein C-II, the activator protein for lipoprotein lipase, was present and functional. Apolipoprotein C-III(1), however, was not detected in the VLDL fraction, a finding previously reported in patients with abetalipoproteinemia. Fecal excretion of cholesterol was almost twice normal; total sterol balance was increased by congruent with40%. The unusual features in the proband that distinguish him from previously described cases and from his affected first-degree relatives suggested that, in addition to the basic gene defect affecting LDL metabolism, he might have a second abnormality affecting clearance of chylomicrons and VLDL. The ratio of apolipoprotein E(3) to E(2) in his VLDL fraction was 0.93, just below the lower limit of normal, suggesting heterozygosity for E(3) deficiency. Whether or not this contributes to his hypertriglyceridemia remains to be established.
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PMID:Metabolic studies in an unusual case of asymptomatic familial hypobetalipoproteinemia with hypolphalipoproteinemia and fasting chylomicronemia. 22 46

The monolayer technique has been used to study the interaction of lipids with plasma apolipoproteins. Apolipoprotein C-II and C-III from human very low density lipoproteins, apolipoprotein A-I from human high density lipoproteins and arginine-rich protein from swine very low density lipoproteins were studied. The injection of each apoprotein underneath a monolayer of egg phosphatidy[14C]choline at 20 mN/m caused an increase in surface pressure to approximately 30 mN/m. With apolipoprotein C-II and apolipoprotein C-III there was a decrease in surface radioactivity indicating that the apoproteins were removing phospholipid from the interface; the removal of phospholipid was specific for apolipoprotein C-II and apolipoprotein C-III. Although there was a removal of phospholipid from the monolayer, the surface pressure remained constant and was due to the accumulation of apoprotein at the interface. The rate of surface radioactivity decrease was a function of protein concentration, required lipid in a fluid state and, of the lipids tested, was specific for phosphatidylcholine. Cholesterol and phosphatidylinositol were not removed from the interface. The addition of 33 mol% cholesterol to the phosphatidylcholine monolayer did not affect the removal of phospholipids by apolipoprotein C-III. The addition of phospholipid liposomes to the subphase greatly facilitated the apolipoprotein C-II-mediated removal of phospholipid from the interface. Although apolipoprotein A-I and arginine-rich protein gave surface pressure increases, phospholipid was only slightly removed fromthe interface by the addition of liposomes. Based on these findings, we conclude that the apolipoproteins C interact specifically with phosphatidylcholine at the interface. This interaction is important as it relates to the transfer of the apolipoproteins C and phospholipids from very low density lipoproteins to other plasma lipoproteins. The addition of human plasma high density lipoproteins or very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of phosphatidyl[14C]choline from the interface 3--4 fold. Low density lipoproteins did not affect the rate of decrease. During lipolysis of very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of with the lipid monolayer. Lipolysis experiments were performed in a monolayer trough containing a surface film of egg phosphatidyl[14C]choline and a subphase of very low density lipoproteins and bovine serum albumin. Lipolysis was initiated by the addition of purified milk lipoprotein lipase to the subphase. As a result of lipolysis, there was a decrease in surface radioactivity of phosphatidylcholine. The pre-addition of high density lipoproteins decreased the rate of decrease in surface radioactivity...
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PMID:Interaction of plasma apolipoproteins with lipid monolayers. 22 40

In this study we have investigated the effects of very low density lipoprotein (VLDL) lipolysis on the removal of radiolabeled apolipoprotein C-II and apolipoprotein C-III-1 from in vitro lipolyzed lipoproteins. Lipolysis was carried out in vitro using lipoprotein lipase purified from bovine milk, and mixtures with or without plasma. Lipoproteins were isolated by ultracentrifugation and by gel filtration. Labeled apo-C-II and apo-C-III-1 distributed among plasma lipoproteins, predominantly VLDL and high density lipoprotein (HDL). Lipolysis induced transfer of apo-C-II and apo-C-III-1 from VLDL to HDL. The transfer was proportional to the extent of triglyceride hydrolysis, and similar for the two apoproteins. The apo-C-II/apo-C-III-1 radioactivity ratio did not change in either VLDL or the fraction of d greater than 1.006 g/ml during the progression of the lipolytic process. Similar observations were recorded while using plasma-devoid lipolytic systems. Gel filtration of incubation mixtures, on 6% agarose, revealed that the removal of labeled apo-C molecules from VLDL is not a consequence of either centrifugation or high salt concentration. These results suggest that there is no preferential removal of apo-C-II or apo-C-III-1 from lipolyzed VLDL particles. They further indicate that the ratio of apo-C-II to apo-C-III-1 does not regulate the extent of lipolysis of different VLDL particles, at least in VLDL isolated from normolipidemic humans.
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PMID:Very low density lipoprotein. Removal of Apolipoproteins C-II and C-III-1 during lipolysis in vitro. 22 2

Apolipoprotein C-II, a protein found associated with all major classes of plasma lipoproteins, is a potent activator of the enzyme lipoprotein lipase. We have prepared the maleyl, citraconyl and succinyl derivatives of apolipoprotein C-II, and compared the capacities of the intact and tryptically cleaved proteins to activate lipoprotein lipase. The NH2-terminal 50 residue peptide proved virtually inactive, even after removal of the masking groups from the citraconyl derivative. The COOH-terminal 29 residue peptides of maleyl and citraconyl apolipoprotein C-II were more active than the corresponding succinylated peptide. After deacylation of the citraconyl derivative, the COOH-terminal peptide had maximal activity as great as apolipoprotein C-II, although the profile of activation remained dissimilar at low activator concentrations.
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PMID:Activation of lipoprotein lipase by native and acylated peptides of apolipoprotein C-II. 46 17

A 59-year-old man with severe hypertriglyceridemia and no post-heparin lipolytic activity was studied because of a marked fall in plasma triglyceride concentrations after a blood transfusion. An apolipoprotein activator (apolipoprotein C-II) for lipoprotein lipase could not be detected by polyacrylamide-gel electrophoresis of apoproteins, immunodiffusion of the plasma against anti-apolipoprotein CII or activation assays for lipoprotein lipase. Furthermore, the patient's triglyceride-rich lipoproteins would not serve as substrate for lipoprotein lipase. The patient had latent post-heparin lipolytic activity, which appeared after the addition of apolipoprotein CII to the post-heparin plasma. After a transfusion of 1 unit of plasma from a normal subject the patient's plasma triglycerides fell, within one day, from 1000 to 250 mg per deciliter and remained below preinfusion concentrations for six days. We conclude that this patient's hyperlipoproteinemia resulted from a deficiency of apolipoprotein C-II.
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PMID:Hypertriglyceridemia associated with deficiency of apolipoprotein C-II. 56 77


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