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)

The kinetics of product inhibition of bovine milk lipoprotein lipase (LPL) were studied in a system of emulsified trioleoylglycerol (TG) at different fixed initial concentrations of oleic acid [( OA]0) without a fatty acid (FA) acceptor. In the absence of apolipoprotein C-II (C-II), the apparent Vmax and the nH(TG) (the slope of the corresponding Hill plot for TG) of 1.82 decreased by about 52% and [TG]0.5 increased 13-fold by raising the [OA]0 to 0.3 mM. At low [OA]0, product inhibition was competitive with respect to TG: the nH(OA) averaged 1.1, and [OA]0.5 was increased about 2-fold by TG. At the higher [OA]0, nH(OA) was 3.5, and TG had no effect on [OA]0.5. In the presence of 3 micrograms/mL C-II, the apparent Vmax was 4.3-7.1-fold higher than in its absence, and the nH(TG) was 2.45. Both parameters decreased by only 20-25%, and [TG]0.5 increased only 3-fold at an [OA]0 of 0.3 mM. Conversely, nH(OA) decreased by 35% and [OA]0.5 increased 6-fold by increasing TG concentrations. Similar kinetics were observed with very low density lipoproteins (VLDL). At saturating TG and varying C-II concentrations, nH(C-II) was 1.78, and product inhibition was found to be competitive with respect to C-II. At the [OA]0 employed, the FA had no effect on enzyme binding to TG emulsions, and there was no evidence that LPL catalyzes the reverse reaction. It is concluded that (a) the LPL kinetics are those of a multisite enzyme that probably has three high-affinity binding sites for TG, two for C-II, and four for OA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Kinetics of product inhibition and mechanisms of lipoprotein lipase activation by apolipoprotein C-II. 365 6

The effect of apolipoprotein C-II (apoC-II) and a synthetic fragment of apoC-II corresponding to residues 56-79 on the lipoprotein lipase (LpL) catalyzed hydrolysis of trioleoylglycerol in a monolayer of egg phosphatidylcholine and of dipalmitoylphosphatidylcholine vesicles was examined. Synthetic peptide 56-79, which does not associate with lipid, did not activate LpL at surface pressures greater than 30 mN/m; apoC-II is active up to 34 mN/m. However, acylation of the NH2-terminus of peptide 56-79 with palmitoyl chloride gave nearly identical LpL activating properties as compared to apoC-II. We conclude that at high surface pressures the lipid-binding region of apoC-II (residues 44-55) plays an essential role in LpL activation.
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PMID:Activation of lipoprotein lipase by N-alpha-palmitoyl (56-79) fragment of apolipoprotein C-II. 372 48

Mixed acyl chain phosphatidylcholine molecules in Triton N-101 micelles were employed as substrates for lipoprotein lipase to test which substrate acyl chain has the greatest effect on activation of the enzyme by apolipoprotein C-II. The phospholipase A1 activity of lipoprotein lipase was measured by pH-stat. The activation factor (lipoprotein lipase activity plus apolipoprotein C-II/activity minus apolipoprotein C-II) increased monotonically with apolipoprotein C-II concentration up to 1 microM apolipoprotein C-II at an enzyme concentration of 0.01 microM. The maximal activation factor for phosphatidylcholine substrate molecules with sn-2 acyl chain lengths of 14 averages 14.8. By contrast, for sn-2 acyl chain lengths of 16 the activation factor was 29.2. Varying the sn-1 acyl chain length had no significant effect on the activation factor. The chain-length dependence of the activation factor is similar with the apolipoprotein C-II peptide fragment comprising residues 56-79, which does not include the lipid-binding region of apolipoprotein C-II. These data are consistent with a model for activation of lipoprotein lipase in which residues 56-79 bind to lipoprotein lipase and alter the interaction of the sn-2 acyl chain of the phosphatidylcholine (PC) substrate or the lysoPC product within the activated state complex.
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PMID:Fatty acyl chain specificity of phosphatidylcholine hydrolysis catalyzed by lipoprotein lipase. Effect of apolipoprotein C-II and its (56-79) synthetic fragment. 375 5

The effects of infant diet (breast milk or formula containing 2, 30 or 60 mg/dl cholesterol) and subsequent dietary cholesterol (0.02, 1.0 or 1.7 mg/kcal) and fat (saturated or unsaturated) on heparin-releasable lipolytic activity from omental adipose tissue was estimated from 99 baboons of 5-8 years of age. This lipase activity was characterized as lipoprotein lipase based on salt inhibition and apolipoprotein C-II activation. Lipoprotein lipase activity released from adipose tissue by heparin was significantly (P less than 0.002) lower in high cholesterol-fed baboons than in those fed low cholesterol. Most of this difference was due to impaired long-term heparin release of lipoprotein lipase. Adipose tissue lipoprotein lipase increased with increasing fat cell size regardless of diet, but there was no effect of diet on adipocyte size. There were no significant effects of infant cholesterol intake nor adult saturated or unsaturated fat on lipoprotein lipase activity. Adult baboons breast fed as infants had lower adipose tissue lipoprotein lipase activity (P less than 0.07) than adults fed formula as infants.
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PMID:Effects of dietary cholesterol on adipose tissue lipoprotein lipase in the baboon. 376 86

To clarify the possibility that brain microvessels could utilize very low density lipoprotein (VLDL)-triglyceride, the hydrolysis of [14C] triolein in VLDL by rat brain microvessels was examined. The rat brain microvessels were prepared under microscopy. In the homogenate, triolein hydrolyzing activity was observed only in the presence of apolipoprotein C-II. That activity was diminished by the addition of 1 M NaCl. [14C] triolein incorporated in VLDL was hydrolyzed time- dependently. These results suggested that there exists lipoprotein lipase in brain microvessels and the brain can utilize VLDL triglyceride as a source of fatty acids.
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PMID:Existence of lipoprotein lipase in rat brain microvessels. 377 67

Lipoprotein lipase [EC 3.1.1.34, LpL] was purified from human postheparin plasma (PHP) almost to homogeneity (a 210,000-fold purification) using columns of heparin-Sepharose, hydroxylapatite, and concanavalin A-Sepharose, and its properties were compared with the purified bovine milk LpL. The specific activity of the PHP-LpL was 26 mmol free fatty acids (FFA)/h/mg of protein at 37 degrees C; close to that of bovine milk LpL (35 mmol FFA/h/mg). For both enzyme preparations, the pH optimum (about 8.7) and the inhibition by sodium chloride were almost the same. The apparent Michaelis constants were also similar; 2.5 mM for human PHP-LpL and 2.1 mM for bovine milk LpL. The apparent molecular weight of the purified human PHP-LpL was 58,000 by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, slightly larger than that of the bovine milk LpL (56,000). Although the amino acid composition of the two LpL preparations had only slight differences, antibody raised against bovine milk LpL cross-reacted very weakly with purified human PHP-LpL. With 1% bovine serum albumin, bovine milk LpL was highly stable, but the human PHP-LpL was unstable; it lost 60% of its activity within 60 min at 0 degrees C. In the absence of apolipoprotein C-II (apo C-II), the activity of human PHP-LpL was very weak. However, human PHP-LpL was activated by apo C-II more strongly than bovine milk LpL; the fold activation of human PHP-LpL by apo C-II was 7-8 times that of bovine milk LpL. The apparent Km value of human PHP-LpL for apo C-II (1.00 +/- 0.58 microM) was larger than that of bovine milk LpL (0.15 +/- 0.03 microM).
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PMID:Purification and characterization of lipoprotein lipase from human postheparin plasma and its comparison with purified bovine milk lipoprotein lipase. 378 53

The administration of Intralipid to starved adult rats induces the appearance of lipoprotein lipase (LPL)-like activity in the liver, whereas the so-called hepatic triacylglycerol lipase is unaffected. This LPL-like activity is eluted by 1.5 M-NaCl from heparin-Sepharose columns. This partially purified fraction is inhibited by 1.0 M-NaCl (91%) and by 1.0 mg of protamine sulphate/ml (79%), whereas it is stimulated 69-fold by the presence of 8.0 micrograms of apolipoprotein C-II/ml and inhibited by anti-LPL antibodies. We conclude that Intralipid administration induces the appearance of LPL activity in livers of starved adult rats. Its possible origin is discussed.
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PMID:Intralipid administration induces a lipoprotein lipase-like activity in the livers of starved adult rats. 379 76

A human cell line established from a patient of an acute monocytic leukemia (THP-1) retained an ability to synthesize and secrete plasma apolipoprotein E like protein. The protein was identified with monospecific antibody raised against human plasma apolipoprotein E. The cells also secreted lipoprotein lipase (EC 3.1.1.34). The enzyme was characterized as lipoprotein lipase on the basis of the requirement of apolipoprotein C-II as an activator and the inhibition of its activity by sodium chloride. The secretion of both apolipoprotein E and lipoprotein lipase was markedly enhanced in the process of differentiation into macrophage-like cells by the addition of 4 beta-phorbol 12 beta-myristate 13 alpha-acetate.
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PMID:Cells of a human monocytic leukemia cell line (THP-1) synthesize and secrete apolipoprotein E and lipoprotein lipase. 385 20

Previous work has shown that nascent hepatic very-low-density lipoproteins (VLDL) in the rat are biosynthesized without the obligatory co-factor (apolipoprotein C-II) for lipoprotein lipase-mediated hydrolysis of their core triacylglycerols. Upon secretion, apolipoproteins C-II and C-III are rapidly transferred to the particles from high-density lipoprotein (HDL) within the space of Disse and upon the entry into the plasma. Here we extend those studies to include observations on the apolipoprotein E content and lipid composition of nascent hepatic VLDL before and after exposure to plasma components. We have elected to use hepatic secretory vesicle VLDL rather than liver perfusate VLDL as truly representative of the nascent lipoproteins. Nascent VLDL from fed rats has an apolipoprotein B/E ratio of 6.6 +/- 0.5, whereas that from fasted animals is 13.9 +/- 2.3. Incubation of nascent VLDL from fed and fasted rats with d greater than 1.063 g/ml rat serum, HDL or the d greater than 1.21 g/ml fraction resulted in a mass transfer of apolipoprotein E to the VLDL such that the apolipoprotein B/E ratio decreased to at least that of serum VLDL (3.4 +/- 0.3). The d greater than 1.21 g/ml fraction appeared to contain a species of apolipoprotein E which most actively transferred to VLDL. The acquisition of apolipoprotein E by nascent secretory vesicle VLDL was attended by a loss of phospholipids, particularly the C40 (stearoylarachidonyl) molecular species, and an increase in the cholesterol-to-phospholipid ratio from 0.11 +/- 0.01 to 0.18 +/- 0.03. No evidence was obtained to suggest a simultaneous acquisition of cholesteryl esters upon incubation of nascent VLDL with VLDL-free serum. We conclude that nascent hepatic VLDL is modified after secretion by acquisition of apolipoproteins C-II, C-III and E with a concomitant loss of phospholipids.
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PMID:Post-secretory acquisition of apolipoprotein E by nascent rat hepatic very-low-density lipoproteins in the absence of cholesteryl ester transfer. 394 May 34

The lipolytic activities of heart tissue towards full and partial acylglycerols were characterized. Tissue lysosomal, acid lipase activity (pH 4.8) was inhibited by high salt, protamine sulfate, NaF, MgATP, Triton X-100, serum and the esterase-inhibitor diethylparanitrophenyl phosphate. The tissue neutral triacylglycerol lipase activity (pH 7.4) was recovered predominantly in the microsomal and soluble fractions and exhibited essentially identical properties towards activators (serum, apolipoprotein C-II) and reagents (NaCl, Triton X-100, NaF, MgATP and diethylparanitrophenyl phosphate) relative to vascular lipoprotein lipase, except for protamine sulfate which increased the serum-stimulated neutral triacylglycerol lipase activity. Triacylglycerol hydrolysis at acid pH was incomplete, whereas at neutral pH full hydrolysis occurred. Myocardial mono- and diacylglycerol lipase activities, with pH optima of 8.0 and 7.4, respectively, were recovered in the microsomal fraction. They differed immunologically from neutral lipase and lipoprotein lipase and did not bind to heparin-Sepharose 4B. They were kinetically different, partially inhibited by NaCl and differentially affected by protamine sulfate. NaF, Triton X-100 and diethylparanitrophenyl phosphate. Our data suggest that endogenous hydrolytic activity against full and partial acylglycerols is mediated by separate enzymes.
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PMID:Characterization of mono-, di- and triacylglycerol lipase activities in the isolated rat heart. 394 May 38


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