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)

Two enzymes, lipoprotein lipase and hepatic triglyceride lipase, are involved in the hydrolysis of triglycerides from chylomicrons and very low density lipoprotein (VLDL). Lipoprotein lipase has an absolute requirement for apolipoprotein CII for activity. Three inborn errors of metabolism which give rise to hypertriglyceridaemia have been described. The biochemical and clinical aspects of these disorders, lipoprotein lipase deficiency (familial type I hyperlipoproteinaemia), hepatic triglyceride lipase deficiency and apo-CII deficiency are discussed.
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PMID:Lipase deficiencies. 314 84

Apolipoproteins play major roles in regulating lipoprotein synthesis and catabolism. Apolipoprotein AI activates the lecithin cholesterol acyltransferase, apolipoprotein CII and CIII regulate the lipoprotein lipase, and apolipoprotein B-100, B-48, and E control the cholesterol uptake into hepatic and extrahepatic cells. Therefore, investigating the alterations of lipoprotein metabolism in disease states at the apolipoprotein level may give increased insight into the underlying mechanisms of lipoprotein changes and provide better understanding about the premature development of the atherogenic process.
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PMID:Lipoproteins and apolipoproteins. Composition, metabolism, and association with coronary heart disease. 352 5

Apolipoprotein C-II plays a major role in lipid metabolism as a cofactor for lipoprotein lipase, the enzyme involved in the hydrolysis of triglyceride-rich lipoproteins. Apo-C-II is initially synthesized as a 101 amino acid protein that undergoes subsequent cotranslational cleavage of a signal peptide. Post-translational processing of apo-C-II has not been previously described. In this manuscript we identify four major plasma isoforms of apo-C-II by two-dimensional gel electrophoresis and immunoblot analysis that result from post-translational modification of apo-C-II. Neuraminidase studies have shown that two of these isoforms are early secreted sialic acid containing glycoproteins. Amino acid compositional and amino-terminal analysis have established that the major plasma isoform of apo-C-II is proapo-C-II. Proapo-C-II undergoes proteolytic cleavage of its amino-terminal hexapeptide to generate the mature form of apo-C-II. Thus, apo-C-II appears to be secreted as a carbohydrate containing proprotein that then undergoes deglycosylation and proteolytic cleavage to generate mature apo-C-II, a minor isoform in plasma. An improved understanding of the structural relationship of the various plasma isoforms of apo-C-II will help to elucidate the mechanisms involved in normal, as well as defective, processing of apo-C-II.
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PMID:Human preproapolipoprotein C-II. Analysis of major plasma isoforms. 352 27

It is known that hypertriglyceridemia is associated with the elevation of plasma apolipoprotein CII (apoCII). In an attempt to look at the relationship between the two, the present study was conducted. We examined 30 patients with hypertriglyceridemia (TG, 210 to 9,127 mg/dL) and ten normolipidemic controls. Hypertriglyceridemic patients included 7 of type I hyperlipoproteinemia (HL), 17 of type IV, and 6 of type V. Plasma apoCII was measured by the single radial immunodiffusion method. Major cause for any difference in plasma apoCII could be attributed to differences in the TG-rich lipoproteins. Since a model for the lipoprotein structure indicates that TG-rich lipoproteins are spherical, with apoCII as a surface component and TG as a core substance, we calculated the square roots and the cubic roots of the values of apoCII and TG to make comparison possible. When the two variables were plotted on the X and Y axes respectively, we obtained the regression line of square root of apoCII = 0.37 X 3 the square root of TG - 0.03 with a correlation coefficient of r = .95 (P less than 0.001). The result indicates that a lipoprotein structural model accounts well for the relationship between apoCII and TG. Although a previous report suggested a compensatory increase of apoCII in lipoprotein lipase deficiency, our patients with type I HL had apoCII levels similar to those who had comparable levels of plasma TG.
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PMID:Plasma apolipoprotein CII levels in hypertriglyceridemia. 373 15

The triacylglycerol hydrolyase and phospholipase A1 activities of bovine milk lipoprotein lipase toward long-chain fatty acyl ester substrates were investigated with monomolecular lipid films containing trioleoylglycerol and phosphatidylcholine. In a monolayer of egg phosphatidylcholine containing 3 mol% [14C]trioleoylglycerol, and in the presence of apolipoprotein C-II, a 79 amino acid activator protein for lipoprotein lipase, enzyme activity was maximal at a surface pressure of 21-22 mN X m-1 (37 mumol oleic acid released/h per mg enzyme); enzyme activity was enhanced 9-fold by apolipoprotein C-II. At surface pressures between 22 and 30 mN X m-1, lipoprotein lipase activity decreased over a broad range and was nearly zero at 30 mN X m-1. Apolipoprotein C-II and the synthetic fragments of the activator protein containing residues 56-79, 51-79 and 44-79 were equally effective at 20 mN X m-1 in enhancing lipoprotein lipase catalysis. However, at surface pressures between 25 and 29 mN X m-1, only apolipoprotein C-II and the phospholipid-associating fragment containing residues 44-79 enhanced enzyme catalysis. The effect of apolipoprotein C-II and synthetic peptides on the phospholipase A1 activity of lipoprotein lipase was examined in sphingomyelin:cholesterol (2:1) monolayers containing 5 mol% di[14C]myristoylphosphatidylcholine. At 22 mN X m-1, apolipoprotein C-II and the synthetic fragments containing residues 44-79 or 56-79 enhanced lipoprotein lipase activity (70-80 nmol/h per mg enzyme). In contrast to trioleoylglycerol hydrolysis, the synthetic fragments were not as effective as apolipoprotein C-II enhancing enzyme activity towards di[14C]myristoylphosphatidylcholine at higher surface pressures. We conclude that the minimal amino acid sequence of apolipoprotein C-II required for activation of lipoprotein lipase is dependent both on the lipid substrate and the packing density of the monolayer.
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PMID:Interaction of synthetic peptides of apolipoprotein C-II and lipoprotein lipase at monomolecular lipid films. 394 62

Interfacial catalysis of hepatic triacylglycerol lipase (H-TGL) and lipoprotein lipase (LpL) isolated from human post-heparin plasma was investigated with mixed monolayers of trioleoylglycerol (TO) and egg phosphatidylcholine. Rates of enzyme catalysis were dependent on surface pressure, substrate concentration, apoC-II (the activator protein for LpL), and cholesteryl oleate (CO). LpL showed a surface pressure optimum between 22 and 24 mN m-1, whereas H-TGL activity decreased at pressures greater than 20 mN m-1. LpL activity was enhanced greater than 10-fold by apoC-II; 1 M NaCl inhibited enzyme activity. ApoC-II, apoC-III, apoA-I, apoA-II, and 1 M NaCl had no effect on H-TGL activity. The substrate (TO) dependency was different for the two lipases. For LpL, there was a marked enhancement of enzyme activity between 2 and 4 mol % TO, whereas for H-TGL, enzyme activity increased linearly between 1 and 10 mol % TO. LpL activity toward monolayers containing 2 mol % TO was enhanced 2.6-fold by the addition of 5 mol % CO; cholesteryl ester had no effect on H-TGL activity. These findings suggest that the two lipolytic enzymes have different interfacial properties, which may have relevance to the rates of hydrolysis of triacylglycerols at a lipoprotein interface.
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PMID:Comparison of the triacylglycerol hydrolase activity of human post-heparin plasma lipoprotein lipase and hepatic triacylglycerol lipase. A monolayer study. 396 63

Lipoprotein lipase appears to function as the mechanism by which dietary vitamin E (tocopherol) is transferred from chylomicrons to tissues. In patients with lipoprotein lipase deficiency, more than 85% of both the circulating triglyceride and tocopherol is contained in the chylomicron fraction. The studies presented here show that the in vitro addition of bovine milk lipoprotein lipase (lipase) to chylomicrons in the presence of human erythrocytes or fibroblasts (and bovine serum albumin [BSA]) resulted in the hydrolysis of the triglyceride and the transfer of both fatty acids and tocopherol to the cells; in the absence of lipase, no increase in cellular tocopherol was detectable. The incubation system was simplified to include only fibroblasts, BSA, and Intralipid (an artificial lipid emulsion containing 10% soybean oil, which has gamma but not alpha tocopherol). The addition of lipase to this system also resulted in the transfer of tocopherol (gamma) to the fibroblasts. Addition of both lipase and its activator, apolipoprotein CII, resulted in a further increase in the cellular tocopherol content, but apolipoprotein CII alone had no effect. Heparin, which is known to prevent the binding of lipoprotein lipase to the cell surface membrane, abrogated the transfer of tocopherol to fibroblasts without altering the rate of triglyceride hydrolysis. Thus, in vitro tocopherol is transferred to cells during hydrolysis of triglyceride by the action of lipase, and for this transfer of tocopherol to occur, the lipase itself must bind to the cell membrane.
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PMID:Bovine milk lipoprotein lipase transfers tocopherol to human fibroblasts during triglyceride hydrolysis in vitro. 399 53

Human apolipoprotein (apo) C-II, a 79 amino acid protein, functions as a cofactor for lipoprotein lipase, the enzyme which catalyzes the hydrolysis of plasma triglycerides. The chromosomal location of apoC-II has been determined by filter hybridization analysis of human-mouse hybrid cells. Southern blots of DNA from 21 human-mouse hybrid cells were hybridized with a 190 base pair nick translated probe prepared from a Hinf I digest of an apoC-II cDNA clone. Without exception, ApoC-II segregated with chromosome 19 thus establishing synteny with the apoE and LDL receptor genes known to be localized to this chromosome. The localization of the apoC-II gene to chromosome 19 will permit more detailed analysis of the genomic organization and linkages of the apolipoprotein genes.
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PMID:The localization of the gene for apolipoprotein C-II to chromosome 19. 608 9

Apolipoprotein C-II (apoC-II), a 79 amino acid protein, is a cofactor for lipoprotein lipase, the enzyme which catalyzes the lipolysis of triglycerides on plasma chylomicrons and VLDL. Patients with apoC-II deficiency have marked elevations in plasma triglycerides, chylomicrons, VLDL, and a type I hyperlipoproteinemia. In order to evaluate the molecular defect in apoC-II deficiency, genomic DNA was analyzed using Southern Blot from 2 independent apoC-II deficient patients and compared to normal controls. Restriction digests of genomic DNA were performed with five different enzymes and the restriction fragments analyzed utilizing a 354 base pair nick-translated apoC-II probe for hybridization following Southern blotting. The restriction fragments varied from 0.8 to 21 Kb, and the pattern with normal DNA was identical to that of the two apoC-II deficient patients. The present study reveals that the apoC-II gene is present in patients with apoC-II deficiency. In addition, no insertional or deletional polymorphism was detected in the apoC-II gene of apoC-II deficient patients.
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PMID:Analysis of the apoC-II gene in apoC-II deficient patients. 609 89

In view of the high incidence of hyperlipidemia and the low sialic acid content in the membranes of diabetics, we analyzed the percentage composition of apolipoprotein CII, known as an activator of lipoprotein lipase, and a subspecies of apolipoprotein CIII, an inhibitor of lipoprotein lipase, in triglyceride-rich lipoproteins. CIII can be sub-divided into three groups, CIII0, CIII1 and CIII2, according to sialic acid content by isoelectric focusing gel. In 82 diabetics, serum lipids and lipids in various lipoprotein fractions differed according to treatment, (diet, oral hypoglycemic drug or insulin). CIIIo/CII showed a positive correlation to plasma triglyceride and cholesterol. In the group receiving oral medication (N = 20), CIIIo/CII vs HDL-cholesterol showed a positive correlation, whereas CIII2/CII vs plasma triglyceride showed an inverse correlation. In the insulin group (N = 25), the percentage of CIIIo in VLDL apo C subspecies was inversely correlated with plasma cholesterol. In 38 diabetics whose HbA1 was also examined, CIIIo/CII increased with elevation of HbA1. CIIIo/CII in diabetics with HbA1 higher than 10% was significantly high compared with the index in other diabetics. The percentage of CIII1 in VLDL apo C subspecies was correlated to HbA1 level positively in the diet group but inversely in the insulin group. These results suggest that lipoprotein metabolism in diabetics may vary according to treatment and the sialylation of apolipoprotein may play an important role in determining the severity of this disease.
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PMID:Lipoprotein metabolism in diabetics treated with diet, oral hypoglycemic drug and insulin. 639 41


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