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)

A tri-, di-, and monoacylglycerol-hydrolyzing enzyme from rat adipose tissue has been detergent-solubilized and separated from monoacylglycerol lipase (H. Tornqvist and P. Belfrage, 1976, J. Biol. Chem. 251, 813-819) and lipoprotein lipase by use of ion-exchange chromatography, broad and narrow pH range electrofocusing and gel chromatography. The final preparation contained several different proteins. One of these, with an apparent minimum molecular weight of 86,000 by SDS-gel electrophoresis, was identified as the enzyme protein of hormone-sensitive lipase: a) the enzyme activity was reproducibly stimulated 50-100% by incubation with cyclic AMP-dependent protein kinase, cyclic AMP and ATP-Mg2+; b) the relative intensity of the Mw 86,000 protein band, and only this, closely paralleled the enzyme activity during narrow pH range electrofocusing and during subsequent gel chromatography of the electrofocusing enzyme peak fraction; c) only the Mw 86,000 protein extensively incorporated 32p from [gamma-32P]ATP after incubation with protein kinase and cyclic AMP. The pI of the enzyme was 6.7, it had the same Stokes radius on Sephadex G 200 as IgG and was 50% inactivated by 10 micron HgCl2, 20 micron PCMB, 50 micron DFP, 10 mM NaF and non-ionic detergents above their critical micellar concentration.
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PMID:Identification and some characteristics of the enzyme protein of the hormone-sensitive lipase from rat adipose tissue. 66 58

Equine plasma lipoproteins were fractionated into VLDL, LDL-1, LDL-2 and HDL by density gradient ultracentrifugation. From each lipoprotein fraction, five apo C like peptides of approx. M(r) 1400, 10000, 9500, 9000 and 8000 were detected by SDS-polyacrylamide gel electrophoresis. After partial purification by Sephadex G-75, one fraction, showing a strong activation of lipoprotein lipase, was further purified by Mono Q anion exchange column. Two of the apo C like peptides (M(r) 10000 and 8000) activated the bovine milk lipoprotein lipase in vitro; only one (M(r) 9500) inhibited the lipolytic activity. This work confirms that many mammals present two apo C-II components with different molecular weights.
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PMID:Characterization of lipoprotein lipase activators from equine plasma. 128 92

After adipocytes were labeled with Na2[35SO4], immunoadsorbed with immobilized antilipoprotein lipase, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography, a labeled band was identified at 59,700 daltons, the molecular mass of chicken lipoprotein lipase (LPL). Excess unlabeled LPL prevented the immunoadsorption of this labeled species, hence the labeled species was determined to be LPL. Digestion of LPL with endo-beta-N-acetylglucosaminidase H (Endo H) caused a shift in mobility of LPL in SDS-PAGE with no loss of radioactivity, whereas digestion with glycopeptidase F resulted in removal of 99% of the radioactivity. Adipocytes cultured with Trans35S-label and tunicamycin produced an LPL species of 52,000 daltons, but tunicamycin abolished the incorporation of 35SO4 into LPL. This established that 35SO4 was incorporated into an N-linked oligosaccharide of LPL. Endo H digestion of pulse-chase labeled LPL revealed the presence of two complex and one high mannose-type N-linked oligosaccharides. A single 35SO4-labeled tryptic peptide was isolated by reverse phase chromatography. The amino acid sequence of the peptide established that the 35SO4 oligosaccharide is conjugated at Asn-45. Behavior of the 35SO4-labeled oligosaccharide on concanavalin A-agarose, sequential exoglycosidase digestion, and chemical analysis of the 35SO4 oligosaccharide confirms that this moiety is of the complex type. Sequential exoglycosidase digestion, thin layer chromatography of the released monosaccharides, and the use of glycosylation inhibitors established that the sulfated sugar is a core N-acetylglucosamine (GlcNAc). The data show that chicken LPL contains two complex and one high mannose N-linked oligosaccharides and that 35SO4 is incorporated into LPL on a GlcNAc residue of a complex oligosaccharide located at Asn-45.
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PMID:Occurrence of sulfate in an asparagine-linked complex oligosaccharide of chicken adipose lipoprotein lipase. 198 32

Lipoprotein lipase (LPL) is an important enzyme in lipid and energy metabolism of all vertebrates. Measurement of its activity in human postheparin plasma has become a standard procedure for diagnosis of Type I hyperlipoproteinemia and other types of hypertriglyceridemias. This paper presents a rapid and simple purification procedure for human lipoprotein lipase and the production of specific polyclonal antibodies. In the isolation procedure, the fat moiety of human milk obtained by centrifugation was delipidated and a buffer-extractable fraction chromatographed sequentially on heparin-Sepharose and phenyl-Sepharose. This three-step procedure provides a high yield of apparently pure LPL with very high specific activity against radiolabeled triacylglycerol substrates. The apparent molecular weight of LPL on SDS-PAGE was 60 kDa. Amino acid analysis and NH2-terminal sequencing proved the identity and the apparent homogeneity of the isolated enzyme. alpha-Lactoferrin and antithrombin III, common contaminants in earlier isolation procedures, were not detectable immunologically. Purified LPL was used to produce in the rabbit a specific polyclonal antiserum that inhibited LPL activity from human postheparin plasma and other tissues. In postheparin plasma from normal individuals, anti-LPL IgG was used in Western blotting to show LPL protein. In preheparin plasma, or in certain patients with Type I hyperlipoproteinemia, no specific signal was detected. The improved purification procedure presented here allows the rapid isolation of human LPL and production of antibodies to the protein, both of which will greatly facilitate future studies of this important enzyme.
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PMID:Rapid and simple isolation procedure for lipoprotein lipase from human milk. 234 Mar 7

Estrogen administration (25 mg/kg body weight) in chicks resulted in a marked elevation of plasma very-low-density lipoprotein (VLDL) triacylglycerol (TG). To determine whether the VLDL produced from estrogen (E)-treated birds is catabolized differently from VLDL of control birds, VLDL-TG kinetic studies were conducted. The [14C]TG-labeled VLDL was prepared by intravenous injection of [14C]palmitate into control and E-treated chicks. The [14C]TG-labeled VLDL prepared from the control (C-VLDL-TG) and E-treated chicks (E-VLDL-TG) were then reinjected into fed and fasted chicks with or without E-treatment. The metabolism of VLDL-TG was found to be different, depending upon whether its donor was the control of E-treated chick. The fractional catabolic rate (FCR) of E-VLDL-TG was significantly (P less than 0.05) lower than that of C-VLDL-TG in both fed and fasted chicks. Compared to the fed state, fasting resulted in significantly (P less than 0.05) increased FCRs of both C-VLDL-TG and E-VLDL-TG. The turnover rate of VLDL-TG was significantly higher in E-treated chicks than in their respective controls. In addition, the endogenously produced VLDL-TG differed in their affinity for lipoprotein lipase in which E-VLDL-TG had a higher Km value for the enzyme than C-VLDL-TG. On agarose gel electrophoresis, the VLDL of E-treated chicks showed beta-mobility and it eluted into two peaks on agarose gel filtration, whereas VLDL of control chicks had a pre-beta-mobility on the former and it eluted into a single peak on the latter. SDS-gel electrophoresis also revealed that the apolipoprotein composition of VLDL from control and E-treated chicks was notably different from each other. Present findings suggest that estrogen treatment results not only in an increased secretion of VLDL but also in the production of different VLDL particles, thereby affecting their clearance from the plasma.
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PMID:Effects of estrogen on very-low-density lipoprotein triacylglycerol metabolism in chicks. 237 10

Apoprotein, lipoprotein and lipid parameters of 36 normolipidemic subjects (23 males, mean age 22.7 +/- 7.6 years; 13 females, mean age 26.2 +/- 9.8 years) receiving oral isotretinoin (mean daily dose 0.73 +/- 0.26 mg/kg body weight) for nodulocystic acne (n = 18), severe acne papulopustulosa (n = 15), gram-negative folliculitis (n = 2) and papulopustular rosacea (n = 1) were monitored before and during isotretinoin therapy at biweekly intervals over a period of 14.6 +/- 5.6 weeks. Pretreatment values of mean plasma triglycerides increased significantly (p less than 0.001) from 81.8 +/- 31.9 mg/dl to 112.4 +/- 38.7 mg/dl (47.4%) during isotretinoin treatment. With respect to the mean percent increase of plasma triglycerides from pretreatment levels, patients were classified as nonresponders (less than 10% triglyceride increase), responders (greater than 10% less than 50% triglyceride increase) and hyperresponders (greater than 50% triglyceride increase), revealing a distribution of 25.0, 36.1 and 38.9%, respectively. Isotretinoin treatment had no influence on the isoelectric focusing pattern of apoprotein E isoforms and C apoproteins. In particular, apoprotein C-II, the cofactor of lipoprotein lipase, was not affected. No correlation between apoprotein E phenotypes (2/3, 3/3, 3/4) and the mean plasma triglyceride increase could be demonstrated. Apoprotein B-48, a marker of chylomicrons and atherogenic chylomicron remnants, could not be detected by SDS-PAGE. On the other hand in 21.0% of patients with preexisting mean lipoprotein Lp(a) levels of 18.1 +/- 12.9 mg/dl a moderate increase of atherogenic Lp(a) to mean levels of 37.0 +/- 22.0 mg/dl was observed. Pretreatment values of very-low-density lipoprotein (VLDL) apoprotein (apo) B (7.5 +/- 2.0 mg/dl), low-density lipoprotein apo B (67.3 +/- 17.5 mg/dl) and total plasma apo B (76.6 +/- 19.0 mg/dl) increased significantly to levels of 10.3 +/- 2.4 mg/dl (p less than 0.001), 75.7 +/- 15.8 mg/dl (p less than 0.10) and 85.9 +/- 17.7 mg/dl (p less than 0.05), respectively. As lipoprotein lipase and hepatic lipase activities have been shown to be unaffected by isotretinoin treatment, our data support the hypothesis that isotretinoin induces hepatic oversecretion of VLDL, a condition resembling type IV hyperlipidemia in diabetics, familial hypertriglyceridemia of familial combined hyperlipidemia.
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PMID:Characterization of apoprotein metabolism and atherogenic lipoproteins during oral isotretinoin treatment. 296 29

Conditioned serum-free medium of Ob17 cells transformed by the middle-T-only gene of polyoma virus (Ob17MT cells) is able to support growth and adipose conversion of the parental Ob17 cells. Conditioned media from 3T3-F442A cells (untransformed preadipocyte clonal line) and MTT4 cells (middle-T-transformed non-preadipocyte clonal line) are inactive. The serum-free conditioned medium of Ob17MT cells is also active on growth and adipose conversion of 3T3-F442A cells. The morphological differentiation of Ob17 cells is accompanied by the expression of early (lipoprotein lipase, LPL) and late (glycerol-3-phosphate dehydrogenase, GPDH) biochemical markers of adipose conversion. Bio-Gel P-60 chromatography and SDS-PAGE have allowed characterization of a mitogenic fraction of apparent MW approximately equal to 28 Kd distinct from an adipogenic fraction of apparent MW less than 10 Kd. This adipogenic fraction is only required for the acquisition of the GPDH activity and is therefore active on terminal differentiation.
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PMID:Transformation of Ob17 cells promotes proliferation and differentiation of Ob17 preadipocytes via distinct extracellular intermediates. 301 89

In newborn rats, lipoprotein lipase (LPL) activity was higher in the liver than in several other tissues, such as heart, diaphragm or lungs, and accounted for about 3% of total LPL activity in the body. There was no significant correlation between LPL activity in liver and in plasma. Thus transport of the enzyme from extrahepatic tissues was probably not the major source of LPL in liver. To study LPL biosynthesis directly, newborn rats were injected intraperitoneally with [35S]methionine, and LPL was isolated by immunoprecipitation and separation by SDS/polyacrylamide-gel electrophoresis. Radioactivity in LPL increased with a similar time course in all tissues studied, including the liver. Substantial synthesis of LPL was also demonstrated in isolated perfused livers from newborn rats, whereas synthesis was low in livers from adult rats. There was strong LPL immunofluorescence in livers from newborn rats, mainly within sinusoids and along the walls of larger vessels. This labelling disappeared after perfusion with heparin, which indicates that much of the enzyme is in contact with blood and can take part in lipoprotein metabolism.
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PMID:Synthesis of lipoprotein lipase in the liver of newborn rats and localization of the enzyme by immunofluorescence. 327 27

Rabbit very low density lipoproteins (VLDL) have been fractionated by heparin sepharose chromatography into two subpopulations: an unretained fraction (UR) and a retained fraction (R). The separation profiles of VLDL from cyclophosphamide treated rabbits differed from those obtained in normal animals: UR fraction was far more important in treated rabbits than in control animals. Comparative studies of the two VLDL subfractions isolated from treated rabbits have been performed. Polyacrylamide gel electrophoresis in presence of urea showed a similar distribution in both fractions of apolipoproteins X, a group of low molecular weight apolipoproteins detected after antimitotic therapy. SDS - polyacrylamide electrophoresis revealed the presence of one form of apolipoprotein B: apo B100 in the VLDL from treated rabbits giving evidence of their hepatic origin. Relative to the R-fraction, the UR-fraction was characterized by an increased triacylglycerol content and a larger diameter as observed by electron microscopy. In vitro incubations with lipoprotein lipase and reisolation of postlipolysis particles suggest that both VLDL fractions can undergo metabolic conversion to LDL. A decrease of lipoprotein lipase activity after treatment, as previously observed, may thus explain the accumulation of the large VLDL.
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PMID:Accumulation of large VLDL in cyclophosphamide treated rabbits. Relationship with lipoprotein lipase deficiency. 340 Dec 26

The effects of N-linked glycosylation on the activation and secretion of lipoprotein lipase were studied in Ob17 cells. The cells were first depleted of any activity and enzyme content by cycloheximide treatment and of precursors of oligosaccharide chains by tunicamycin. The repletion of lipoprotein lipase content was studied in these cells maintained in the presence of tunicamycin after cycloheximide removal. During the repletion phase, the EC50 values of inhibition by tunicamycin (approx. 0.2 microgram/ml) of the incorporation of labeled glucose, mannose or galactose into trichloroacetic acid-insoluble material were found to be identical. Under these conditions, the rate of protein synthesis was maximally decreased by 30%. The results showed clearly that the recovery in lipoprotein lipase activity was parallel to the recovery in hexose incorporation, no activity being recovered in the absence of glycosylation. An inactive form of lipoprotein lipase from tunicamycin-treated cells was detected by competition experiments with mature active lipoprotein lipase for the binding to immobilized antilipoprotein lipase antibodies, as well as by immunofluorescence staining. SDS-polyacrylamide gel electrophoresis and Western blots of cellular extracts and of extracellular media, obtained after tunicamycin-treated cells were exposed to heparin, revealed a single immunodetectable Mr 52 000 protein, whereas a single Mr 57 000 protein was detected in control cells. Therefore, the results indicate that the acquisition by lipoprotein lipase of a catalytically active conformation is linked directly or indirectly to glycosylation. Despite this lack of activation, the lipoprotein lipase molecule was able to migrate intracellularily and to undergo secretion after heparin stimulation of the tunicamycin-treated cells.
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PMID:Maturation and secretion of lipoprotein lipase in cultured adipose cells. II. Effects of tunicamycin on activation and secretion of the enzyme. 351 Jun 67


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