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)

Apolipoprotein C-II (apoC-II), a protein constituent of very low density lipoproteins of human plasma and the activator protein of lipoprotein lipase, has been isolated and its amino acid sequence has been studied. The protein has 78 amino acid residues and is lacking cysteine, cystine, and histidine. Chromatography on Bio-Gel P-30 in 25% formic acid of the cyanogen bromide digest of apoC-II yields three fragments designated as CNBr-I, -II, and -III. They contained 50, 19, and 9 residues, respectively. The alignment of the cyanogen bromide fragments has been established as CNBr-III-I-II by isolation and sequence of the tryptic peptides of the intact protein. The amino acid sequences of the tryptic and CNBr peptides were determined by conventional methods. With this information, it was possible to establish the complete amino acid sequence of apoC-II.
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PMID:Primary structure of very low density apolipoprotein C-II of human plasma. 19 44

A specific, precise, and sensitive double-antibody radioimmunoassay for the measurement of human apolipoprotein CII (apoCII) was developed. ApoCII was labeled with (125)I (chloramine-T) and monospecific antibody was raised in rabbits. No appreciable cross-reactivity with apolipoproteins CI, CIII, AI, AII, low density lipoproteins, and lipoprotein-free plasma was observed. Lipoproteins containing apoCII displaced the standard curve in parallel. ApoCII measurement was not affected by pretreatment of plasma with tetramethylurea, ethanol-diethyl ether, or heating. Mean (+/-SE) plasma-immunoreactive apoCII in 47 normotriglyceridemic subjects was 51.8+/-3.2 mug/ml, generally comparable with previous estimates of its concentration by other methods. ApoCII levels in 9 subjects with type IIB lipoprotein pattern, 14 with the type IV lipoprotein pattern, and 5 with type V lipoprotein pattern were respectively, 89.9+/-4.6, 85.4+/-6.9, 132.8+/-21.0 mug/ml, all higher than normals (P < 0.001). Plasma apoCII and triglyceride concentrations correlated in normo- and hypertriglyceridemics (r = 0.36 and 0.58, P < 0.05). Plasma triglycerides correlated inversely with the fraction of total apoCII in very low density lipoprotein (VLDL)-free plasma (r = -0.75, P < 0.01). There was no correlation between plasma apoCII and high density lipoprotein cholesterol. In normotriglyceridemics, VLDL apoCII levels correlated with in vitro lipoprotein lipase (LPL) activator activities (r = 0.89, P < 0.01). In hypertriglyceridemic subjects the mean concentrations of apoCII per milligrams VLDL protein, LPL activator activity per milligrams VLDL protein, and LPL activator activity per micrograms VLDL apoCII were all lower than in normotriglyceridemics, P < 0.05. As plasma triglycerides and apoCII increase, apoCII is redistributed from high density lipoprotein to VLDL. However, the amount of apoCII per milligram VLDL protein and its LPL activator potency per milligram VLDL protein are reduced. These factors may contribute to impaired VLDL catabolism.
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PMID:Radioimmunoassay of human apolipoprotein CII. A study in normal and hypertriglyceridemic subjects. 19 19

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

Apolipoprotein C-II (apoC-II), a protein constituent of human very low density lipoproteins, is the activator for lipoprotein lipase (LPL; triacylglycerol acyl-hydrolase, EC 3.1.1.3). The amino acid sequence of the 78 residues of apoC-II has recently been established in this laboratory. To determine the minimal sequence requirements for activation, we have prepared both native and synthetic fragments of apoC-II and tested them for their ability to activate LPL. Cyanogen bromide fragments of apoC-II corresponding to residues 1--9 and 10--59 had little ability to activate LPL. However, the COOH-terminal cyanogen bromide fragment corresponding to residues 60--78 increased hydrolysis 4-fold compared to an average of 9-fold activation for the same concentration of apoC-II. The synthetic peptide containing residues 60--78 prepared by solid-phase techniques enhanced the lipolysis 3-fold. Addition of five residues produced a synthetic fragment 55--78 that enhanced the release of fatty acid 12-fold compared to 13-fold for intact apoC-II. By contrast, the synthetic peptide containing residues 66--78 did not activate. Removal of the three COOH-terminal residues, Gly-Glu-Glu, from fragment 60--78 decreased the ability to activate LPL by greater than 95%. These studies suggest that the maximal activation of LPL by apoC-II requires a minimal sequence contained within residues 55--78.
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PMID:Activation of lipoprotein lipase by native and synthetic fragments of human plasma apolipoprotein C-II. 27 Jul 15

Apolipoprotein C-II (apoC-II) is a small protein found associated with the plasma lipoproteins. It serves a unique function in the activation of the enzyme lipoprotein lipase (triacylglycerol acyl-hydrolase, EC 3.1.1.3). ApoC-II contains a single arginine residue, permitting tryptic cleavage into two peptides after succinylation of the native protein. The succinylated amino-terminal peptide, approximately 50 residues, did not activate lipoprotein lipase. The succinylated carboxyl-terminal peptide, about 29 residues, had significant cofactor activity. Relative to native apoC-II, the maximal activation observed with the succinylated carboxyl-terminal peptide was 50% lower and the concentration required for half-maximal activity was approximately 10 times higher. Mixtures of the carboxyl- and amino-terminal peptides had no more activity than the carboxyl-terminal peptide alone. Localization of functional properties to the carboxyl region is a feature also common to apolipoproteins C-III, A-II, and A-I.
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PMID:Lipoprotein lipase cofactor activity of a carboxyl-terminal peptide of apolipoprotein C-II. 27 57

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

Hepatic triglyceride lipase was isolated from human post-heparin plasma by the method of Ehnholm et al. using modifications which increased the specific activity 12-fold to approximately 3,000 mumol of free fatty acid/h/mg of protein. Lipoprotein lipase with similar specific activity was prepared from the same plasma samples using heparin and concanavalin A affinity chromatography. The molecular weight of hepatic triglyceride lipase (69,000) was slightly greater than that of lipoprotein lipase (67,000) as determined by polyacrylamide electrophoresis in sodium dodecyl sulfate-containing buffers. These proteins had identical amino acid compositions, terminal amino acid residues, and tryptic peptide maps. However, the differences previously described regarding optima of pH and ionic strength and the requirement for apolipoprotein CII (only for lipoprotein lipase) were maintained in the highly purified state. It was found that both proteins contain approximately 8% carbohydrate. Antisera prepared in goats selectively precipitated each activity. Other antisera prepared in chickens reacted with both enzymes, suggesting a common antigenic determinant.
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PMID:A comparison of molecular properties of hepatic triglyceride lipase and lipoprotein lipase from human post-heparin plasma. 64 Oct 46

1. Lipoprotein lipase was purified from pig myocardium by a two-step purification procedure involving (a) the formation of an enzyme-substrate complex and (b) affinity chromatography on Sepharose which contained covalently linked heparin. The purified enzyme gave in sodium dodecyl sulphate-polyacrylamide-gel electrophoresis one main band with an apparent molecular weight of 73 000. The enzyme, which was purified 70 000-fold, had a specific activity of 860 mumol of unesterified fatty acid liberated/h per mg of protein. 2. The purified enzyme hydrolysed [14C]triolein emulsions in the absence of added cofactors but its activity was increased fivefold by adding normal human serum. Of the low-density lipoprotein apoproteins only apolipoprotein CII could be substituted for serum in activating the enzyme. This lipase had maximum activity at 0.05-0.15 M-NaCl. Heparin increased the activity of the purified enzyme twofold at low concentrations, but high concentrations inhibited. The triglyceride lipase of pig myocardium thus resembles lipoprotein lipase purified from adipose tissue and from plasma, but is clearly different from pig hepatic triglyceride lipase.
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PMID:Purification and characterization of lipoprotein lipase from pig myocardium. 123 78

Hydrolysis by endothelial lipases of triacylglycerol-rich lipoproteins of diabetic origin were compared to lipoproteins of non-diabetic origin. The plasma lipoprotein fraction of density < 1.006 g/ml, including chylomicrons and VLDL, were incubated in vitro with post-heparin plasma (PHP) lipases. The lipoproteins of diabetic origin were hydrolysed at a significantly slower rate than lipoproteins from normal rats by the lipoprotein lipase component of PHP. However, if rats were fasted for 16 h prior to lipoprotein recovery, no differences in rates of VLDL hydrolysis were observed. Slower hydrolysis of lipoproteins of diabetic origin reflected a decrease in the apolipoprotein CII/CIII ratio and other changes in the apolipoprotein profile. To assess whether diabetic rats were less able to clear triacylglycerol independent of changes in the nature of the lipoproteins, we monitored the clearance of chylomicron-like lipid emulsions in hepatectomized rats. In vivo, emulsion triacylglycerol hydrolysis was not slowed due to diabetes. However, control and diabetic rats, which had been fasted for 16 h, cleared triacylglycerol at about twice the rate of fed rats. Triacylglycerol secretion rates in diabetic and control rats were similar, whether fed or fasted. We conclude that in streptozocin diabetic rats, hypertriglyceridemia was not due to overproduction of chylomicron- or VLDL-triacylglycerol, nor to decreased endothelial lipase activities. Rather, in fed diabetic rats, the triacylglycerol-rich lipoproteins are poorer substrates for lipoprotein lipase. This may lead to slower formation of remnants which would exacerbate slow remnant removal. VLDL of diabetic origin were hydrolysed as efficiently as VLDL from control donors, suggesting that in the fed state the lipolytic defect may be specific for chylomicrons.
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PMID:Hypertriglyceridemia is exacerbated by slow lipolysis of triacylglycerol-rich lipoproteins in fed but not fasted streptozotocin diabetic rats. 142 Feb 85


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