Rapid effects of isoprenaline, glucagon, pacing and potassium arrest on post-heparin lipoprotein lipase activity in the perfused rat heart.
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ABSTRACT:
SUBMITTER: Simpson J
PROVIDER: S-EPMC1161258 | biostudies-other | 1979 Jul
REPOSITORIES: biostudies-other
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Project description:Lipoprotein lipase and salt-resistant lipase were isolated from human post-heparin plasma. The proteins of human post-plasma lipoprotein lipase and salt-resistant lipase were identified and demonstrated to be immunologically different. Significant differences between the two enzymes in their relative amino acid composition were demonstrated, which indicates that the two enzymes are different proteins. When analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, the enzymes seemed to have monomer molecular weights similar to that of lipoprotein lipase purified from bovine milk.
| S-EPMC1186663 | biostudies-other
Project description:Heparin (5 units/ml) produced a rapid (5-10 min) release of lipoprotein lipase (LPL) into the incubation medium of cardiac myocytes. Preincubation of myocytes for 30 min with 0.01-10 microM-isoprenaline, 100 microM-forskolin or 500 microM-8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate did not increase heparin-releasable LPL activity. Incubation with isoprenaline also did not change cellular LPL activity, even though the catecholamine did increase the phosphorylase a activity ratio.
| S-EPMC1148534 | biostudies-other
Project description:It has been suggested that lipoprotein lipase (LPL) can be assembled into its catalytically active dimeric form only after its oligosaccharide chains have been processed in the Golgi. To study this in a complete organ, LPL was metabolically labelled with [35S]methionine in perfused guinea-pigs hearts. After 10 min pulse-labelling, LPL protein was eluted as two peaks from heparin-agarose: peak 1 at about 0.65 M NaCl, peak 2 at about 0.95 M NaCl. Catalytic activity was associated only with peak 2. Model studies with bovine LPL showed that active dimeric LPL is eluted in peak 2, but after treatments that dissociate the enzyme into inactive monomers it is eluted in peak 1. Pulse-labelled LPL in both peak 1 and peak 2 was fully sensitive to treatment with endoglycosidase (Endo) H. With chase, peak 1 disappeared and peak 2 acquired resistance to Endo H. These findings suggest that core glycosylated LPL is assembled into dimers already in the endoplasmic reticulum and that processing of the oligosaccharide chains occurs after dimerization.
| S-EPMC1134301 | biostudies-other
Project description:1. Intravenous injection of heparin into the trout resulted in the appearance in the plasma of a lipase with the properties of lipoprotein lipase. 2. The enzyme was purified to apparent electrophoretic homogeneity by means of heparin-Sepharose affinity chromatography. The enzyme was eluted with 1.5 M-NaCl and had a specific activity approx. 450-fold that of the post-heparin plasma. 3. The activity of the purified enzyme was inhibited by 1.0 M-NaCl and protamine sulphate and was stimulated between 3- and 8.8-fold by the addition of trout plasma. 4. The activity was strongly stimulated by trout very low density lipoproteins and to a lesser extent by high density lipoproteins. 5. The isolated enzyme fraction gave a single band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and had an apparent subunit M4 of 63 000. 6. These results suggest that the uptake of lipid by the tissues in the trout can occur by a process similar to that in mammals.
| S-EPMC1158289 | biostudies-other
Project description:Heparin-derived deca- and octa-saccharides were subjected to affinity chromatography on lipoprotein lipase-Sepharose and the fractions eluted at high salt concentration were analysed by strong-anion-exchange chromatography. Two high-affinity decasaccharides were isolated and the structure determined by one- and two-dimensional 1H-n.m.r. spectroscopy. The affinities of 3H-labelled low-molecular-mass heparin and size-fractionated deca-, octa-, and hexa-saccharides for lipoprotein lipase immobilized on microtitre plates were determined from saturation curves. From competition experiments the affinities of unlabelled heparins and pure deca- and hexa-saccharide fragments were determined. The binding was size- and charge-dependent, but structural dependency was also indicated. Thus substitution of a 2-O-sulphated L-iduronic acid with D-glucuronic acid was less important than the sulphation pattern of the D-glucosamine residue for affinity for lipoprotein lipase. Heparin inhibits binding of lipoprotein lipase to alpha 2-macroglobulin-receptor/low-density-lipoprotein receptor-related protein. The effects of size, charge and structure for this inhibition were studied. The ability of the heparin fragments to inhibit binding correlated with their affinity for lipoprotein lipase. This indicates that the inhibition of the binding of lipoprotein lipase to alpha 2-macroglobulin-receptor/low-density-lipoprotein receptor-related protein by heparin is exclusively mediated by binding of heparin to lipoprotein lipase.
| S-EPMC1136764 | biostudies-other
Project description:Background and aimsOur aim was to gain insight into the role that lipoprotein lipase (LPL) and hepatic lipase (HL) plays in HDL metabolism and to better understand LPL- and HL-deficiency states.MethodsWe examined the apolipoprotein (apo) A-I-, A-II-, A-IV-, C-I-, C-III-, and E-containing HDL subpopulation profiles, assessed by native 2-dimensional gel-electrophoresis and immunoblotting, in 6 homozygous and 11 heterozygous LPL-deficient, 6 homozygous and 4 heterozygous HL-deficient, and 50 control subjects.ResultsLPL-deficient homozygotes had marked hypertriglyceridemia and significant decreases in LDL-C, HDL-C, and apoA-I. Their apoA-I-containing HDL subpopulation profile was shifted toward small HDL particles compared to controls. HL-deficient homozygotes had moderate hypertriglyceridemia, modest increases in LDL-C and HDL-C level, but normal apoA-I concentration. HL-deficient homozygotes had a unique distribution of apoA-I-containing HDL particles. The normally apoA-I:A-II, intermediate-size (α-2 and α-3) particles were significantly decreased, while the normally apoA-I only (very large α-1, small α-4, and very small preβ-1) particles were significantly elevated. In contrast to control subjects, the very large α-1 particles of HL-deficient homozygotes were enriched in apoA-II. Homozygous LPL- and HL-deficient subjects also had abnormal distributions of apo C-I, C-III, and E in HDL particles. Values for all measured parameters in LPL- and HL-deficient heterozygotes were closer to values measured in controls than in homozygotes.ConclusionsOur data are consistent with the concept that LPL is important for the maturation of small discoidal HDL particles into large spherical HDL particles, while HL is important for HDL remodeling of very large HDL particles into intermediate-size HDL particles.
| S-EPMC5064856 | biostudies-literature
Project description:1. Lipoprotein lipase (EC 3.1.1.34), which was previously shown to bind to immobilized heparin, was now found to bind also to heparan sulphate and dermatan sulphate and to some extent to chondroitin sulphate. 2. The relative binding affinities were compared by determining (a) the concentration of NaCl required to release the enzyme from polysaccharide-substituted Sepharose; (b) the concentration of free polysaccharides required to displace the enzyme from immobilized polysaccharides; and (c) the total amounts of enzyme bound after saturation of immobilized polysaccharides. By each of these criteria heparin bound the enzyme most efficiently, followed by heparan sulphate and dermatan sulphate, which were more efficient than chondroitin sulphate. 3. Heparin fractions with high and low affinity for antithrombin, respectively, did not differ with regard to affinity for lipoprotein lipase. 4. Partially N-desulphated heparin (40-50% of N-unsubstituted glucosamine residues) was unable to displace lipoprotein lipase from immobilized heparin. This ability was restored by re-N-sulphation or by N-acetylation; the N-acetylated product was essentially devoid of anticoagulant activity. 5. Partial depolymerization of heparin led to a decrease in ability to displace lipoprotein lipase from heparin-Sepharose; however, even fragments of less than decasaccharide size showed definite enzyme-releasing activity. 6. Studies with hepatic lipase (purified from rat post-heparin plasma) gave results similar to those obtained with milk lipoprotein lipase. However, the interaction between the hepatic lipase and the glycosaminoglycans was weaker and was abolished at lower concentrations of NaCl. 7. The ability of the polysaccharides to release lipoprotein lipase to the circulating blood after intravenous injection into rats essentially conformed to their affinity for the enzyme as evaluated by the experiments in vitro.
| S-EPMC1162043 | biostudies-other
Project description:Hydrolysis of VLDL triacylglycerol (TG) by lipoprotein lipase (LpL) is a major step in energy metabolism and VLDL-to-LDL maturation. Most functional LpL is anchored to the vascular endothelium, yet a small amount circulates on TG-rich lipoproteins. As circulating LpL has low catalytic activity, its role in VLDL remodeling is unclear. We use pre-heparin plasma and heparin-sepharose affinity chromatography to isolate VLDL fractions from normolipidemic, hypertriglyceridemic, or type-2 diabetic subjects. LpL is detected only in the heparin-bound fraction. Transient binding to heparin activates this VLDL-associated LpL, which hydrolyses TG, leading to gradual VLDL remodeling into IDL/LDL and HDL-size particles. The products and the timeframe of this remodeling closely resemble VLDL-to-LDL maturation in vivo. Importantly, the VLDL fraction that does not bind heparin is not remodeled. This relatively inert LpL-free VLDL is rich in TG and apoC-III, poor in apoE and apoC-II, shows impaired functionality as a substrate for the exogenous LpL or CETP, and likely has prolonged residence time in blood, which is expected to promote atherogenesis. This non-bound VLDL fraction increases in hypertriglyceridemia and in type-2 diabetes but decreases upon diabetes treatment that restores the glycemic control. In stark contrast, heparin binding by LDL increases in type-2 diabetes triggering pro-atherogenic LDL modifications. Therefore, the effects of heparin binding are associated negatively with atherogenesis for VLDL but positively for LDL. Collectively, the results reveal that binding to glycosaminoglycans initiates VLDL remodeling by circulating LpL, and suggest heparin binding as a marker of VLDL functionality and a readout for treatment of metabolic disorders.
| S-EPMC8595799 | biostudies-literature
Project description:Two triacylglycerol lipase activities were characterized after partial purification from pig post-heparin plasma. These two lipase activities were eluted sequentially with a NaCl gradient from columns containing Sepharose with covalently linked heparin. The first lipase activity, which was eluted at 0.75M-NaCl, was not inhibited at 28 degrees C in the presence of 1M-NaCl and was not further activated by plasma apolipoproteins. The absence of this lipase activity from post-heparin plasma from hepatectomized pigs indicates that the liver plays a role in the synthesis of this enzyme. A second lipase activity, which was eluted at 1.2M-NaCl, was inhibited when assayed in the presence of 1.0M-NaCl and was activated 14-fold by an apolipoprotein isolated from human very-low-density lipoprotein. The characteristics are identical with those of lipoprotein lipase purified from pig adipose tissue.
| S-EPMC1164703 | biostudies-other
Project description:Changes in adipose-tissue lipoprotein lipase activity that are independent of protein synthesis were investigated in an incubation system in vitro. Under appropriate conditions at 25 degrees C a progressive increase in the enzyme activity occurs that is energy-dependent. Part of the enzyme is rapidly inactivated when the tissue is incubated with adrenaline or adrenaline plus theophylline. The mechanism of this inactivation appears to be distinct from, and to follow, the activation of the enzyme. A hypothesis is presented to account for the results in terms of an activation of the enzyme during obligatory post-translational processing and a catecholamine-regulated inactivation of the enzyme as an alternative to secretion from the adipocyte.
| S-EPMC1186310 | biostudies-other