scholarly journals Lysosomal triacylglycerol lipase activity in L6 myoblasts and its changes on differentiation

1985 ◽  
Vol 227 (2) ◽  
pp. 583-589 ◽  
Author(s):  
V S Sauro ◽  
H J Klamut ◽  
C H Lin ◽  
K P Strickland
Keyword(s):  
Neutral Lipid ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Thiol Group ◽  
Cell Fractionation ◽  
Marker Enzyme ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Lipid Stores ◽  
Triton X

L6 myoblasts, before fusion, accumulate large stores of neutral lipid when cultured in medium supplemented with fatty acid. Upon fusion to terminally differentiated myotubes, a noticeable decrease in these neutral-lipid stores was observed. Triacylglycerol lipase activity was examined in L6 myoblasts at various stages of cell differentiation to assess a possible role for this enzyme in the above phenomenon. In this first study to demonstrate lipolytic activity in cultured muscle cells, the activity was found to be totally dependent on the presence of a detergent, either Cutscum or Triton X-100, during homogenization. The inhibition by many thiol-specific reagents [N-ethylmaleimide, p-chloromercuribenzoate, iodoacetate, 5,5′-dithiobis-(2-nitrobenzoic acid)] suggest that a thiol group is at or near the active site. The observed acidic pH optimum (5.5-6.0), the acute inhibition by chlorpromazine (a lysosomal lipase inhibitor) and the distribution of lipolytic activity upon cell fractionation (which co-sediments with acid phosphatase, a lysosomal marker enzyme) suggest that the lipase may be of lysosomal origin. Under the optimal conditions described, the triacylglycerol lipase activity of L6 myoblasts was determined to be 2.9 +/- 0.4 nmol of oleic acid released/min per mg of DNA. This activity increased 3-fold, to 9.0 +/- 1.6 nmol/min per mg, in the myotube phase. This increase in lipolytic activity may be responsible for the observed decrease in neutral-lipid stores of differentiating myoblasts.

Characterization of the triacylglycerol lipase activity in three types of rat skeletal muscle

1987 ◽  
Vol 65 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Wayne C. Miller ◽  
Warren K. Palmer ◽  
David A. Arnall ◽  
Lawrence B. Oscai
Keyword(s):  
Skeletal Muscle ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Vastus Lateralis ◽  
High Energy ◽  
Glycolytic Flux ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Triglyceride Lipase

The purpose of this study was to characterize the lipolytic activity of the alkaline triglyceride lipase in homogenates of three types of skeletal muscle obtained from heparin-perfused rat hindlimb. Specifically, the red portion of the vastus lateralis, the white portion of the vastus lateralis, and the soleus muscles were examined. To remove capillary-bound lipoprotein lipase from the capillary beds, muscle was perfused with an erythrocyte-free buffer containing 4% albumin, 5 units of heparin/mL, and 7.5 μM adenosine. Adenosine reduced perfusion pressure from 117 ± 5 to 86 ± 6 mmHg (1 mmHg = 133.32 Pa), providing evidence for an effective vasodilation. This vasodilation increased the amount of lipoprotein lipase removed from the capillary beds. By the end of the experiment, perfusates were lipoprotein lipase-free. Oxygen supply to the perfused hindlimb appeared adequate as evidenced by similar high energy phosphate values for perfused and contralateral control tissues. For example, in soleus muscle, ATP content was 4.5 ± 0.6 vs. 4.2 ± 0.3 μmol/g, ADP concentration was 1.0 ± 0.2 vs. 1.4 ± 0.2 μmol/g, and creatine phosphate level was 12.9 ± 0.7 vs. 11.0 ± 0.6 μmol/g for perfused and contralateral control soleus, respectively. In addition, K+ output by the hindlimb was negligible, while glycolytic flux of perfused muscle was similar to that measured in control tissue. The findings that triglyceride levels of soleus and red vastus lateralis were decreased suggest that endogenous triglyceride was providing energy for the hindlimb during perfusion. Skeletal muscle triglyceride lipase activity was stimulated by serum and heparin, inhibited by NaCl and protamine, and had a pH optimum of 8.1. These results are consistent with the hypothesis that the major lipolytic activity present in the intracellular compartment of skeletal muscle is the alkaline triglyceride lipase with characteristics similar to those of lipoprotein lipase.

Methylamine does not inhibit rates of endogenous lipolysis in isolated myocardial cells from rat heart

1987 ◽  
Vol 65 (2) ◽  
pp. 226-229 ◽  
Author(s):  
Albert Kryski Jr. ◽  
Terje S. Larsen ◽  
Ignasi Ramírez ◽  
David L. Severson
Keyword(s):  
Fatty Acids ◽  
Lipase Activity ◽  
Rat Heart ◽  
Diabetic Rat ◽  
Myocardial Cells ◽  
Acid Lipase ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Rat Hearts ◽  
Lysosomotropic Agent

Triacylglycerol lipase activity with a pH optimum of 5 was present in homogenates of myocardial cells from rat heart. Acid lipase activity was inhibited by serum, heparin, and increased ionic strength. Methylamine, a lysosomotropic agent, did not inhibit the basal or isoproterenol-stimulated rate of endogenous lipolysis as measured by glycerol output from control myocytes. Similarly, accelerated rates of glycerol output that are a consequence of an elevation in the intracellular stores of triacylglycerols in myocytes from diabetic rat hearts and from myocytes prepared with free fatty acids in the isolation solutions were not reduced by methylamine. Therefore, the acid lysosomal triacylglycerol lipase must not be involved in the mobilization of endogenous triacylglycerols in myocardial cells from rat heart.

scholarly journals Complete loss of heparin-releasable triacylglycerol lipase activity after collagenase treatment of the rat liver

1978 ◽  
Vol 172 (1) ◽  
pp. 177-179 ◽  
Author(s):  
J Thomas ◽  
L J Debeer ◽  
G P Mannaerts
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Complete Loss ◽  
Triacylglycerol Lipase ◽  
Collagenase Treatment ◽  
Membrane Bound

Lipolytic activity at pH 8.5-9.5 was lowered by approx. 80% in homogenates from livers perfused with collagenase or heparin. No heparin-releasable lipase activity was detected in hepatocytes isolated by collagenase treatment. It is concluded that crude collagenase completely inactivates the plasma-membrane-bound heparin-releasable lipase.

Modulation by phenobarbital of lipolytic activity in postheparin plasma and tissues of the rat

1982 ◽  
Vol 60 (11) ◽  
pp. 1077-1083 ◽  
Author(s):  
David M. Goldberg ◽  
M. Waheed Roomi ◽  
Alex Yu
Keyword(s):  
Adipose Tissue ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Lipolytic Activity ◽  
Sodium Dodecyl ◽  
Male Rats ◽  
Lipoprotein Lipase Activity ◽  
Protamine Sulphate ◽  
Triacylglycerol Lipase ◽  
Postheparin Lipolytic Activity

Male rats injected with phenobarbital at a dose of 100 mg/kg for 5 days manifested increased postheparin lipolytic activity of fasting plasma. Inhibition studies with protamine sulphate, 1 M NaCl, and sodium dodecyl sulphate revealed that the activities of both lipoprotein lipase and hepatic triacylglycerol lipase were increased in the postheparin plasma of the drug-treated rats. Adipose tissue lipoprotein lipase activity was also increased in the phenobarbital-treated rats. The triacylglycerol lipase activity elutable by heparin from liver slices and the residual activity of liver microsomes increased significantly in the drug-treated rats. Lipoprotein lipase of cardiac muscle and red skeletal muscle was unaltered by phenobarbital treatment. The increased postheparin lipolytic activity of fasting phenobarbital-treated rats seems to be accountable through increased lipoprotein lipase activity of adipose tissue and increased triacylglycerol lipase activity of liver, both of which may contribute to the lowered fasting concentrations of serum triacylglycerol mediated by the drug, as previously reported.

scholarly journals Triacylglycerol Lipase Activities of Cultured Rat L6 Myoblasts

1985 ◽  
Vol 38 (1) ◽  
pp. 41
Author(s):  
RK Tume ◽  
F D Shaw
Keyword(s):  
Lipoprotein Lipase ◽  
Cell Lines ◽  
Lipase Activity ◽  
Maximum Velocity ◽  
Acid Lipase ◽  
Ph Optimum ◽  
Triacylglycerol Lipase ◽  
Inhibitory Component ◽  
Cell Homogenate ◽  
Hydrolysis Of

The utilization of exogenous triacylglycerol by fusing and non-fusing rat L6 myoblasts grown in culture was investigated. Although small quantities of triacylglycerol were accumulated by both cell lines during an incubation of 2 h, no evidence could be found for the presence of lipoprotein lipase, either in the cells or released into the medium. Cell homogenate studies confirmed the absence of lipoprotein lipase but revealed the presence of an acid lipase having a pH optimum at 4�6. Acid lipase activity was mainly associated with a 15 000 g pellet and was capable of hydrolysing triolein at maximum velocity in the millimolar range. Unlike lipoprotein lipase, acid lipase was strongly inhibited by serum and preliminary investigations suggest that the inhibitory component of serum is located amongst the higher density lipoproteins. It is likely that the acid lipase is of lysosomal origin and is responsible for the hydrolysis of internalized triacylglycerol for subsequent utilization by the cell.

The specificity of sialyltransferase activity in smooth membrane fractions of embryonic chicken liver

1981 ◽  
Vol 59 (3) ◽  
pp. 171-180 ◽  
Author(s):  
Brad Bendiak ◽  
Sara E. Zalik
Keyword(s):  
Marker Enzyme ◽  
Temperature Optimum ◽  
Ph Optimum ◽  
Acid Glycoprotein ◽  
Acetylneuraminic Acid ◽  
Sialyltransferase Activity ◽  
Acceptor Specificity ◽  
Embryonic Chicken ◽  
Smooth Membrane ◽  
Triton X

Smooth membrane preparations of 13-day embryonic chicken livers, characterized by electron microscopy and marker enzyme analyses, have been found to contain sialyltransferase activity which displayed precise acceptor specificity. One sialyltransferase transferred N-acetylneuraminic acid (NANA) to galβ1 → 4glcNAcβ1 → R structures. Evidence based on competition studies suggests that a second enzyme is present transferring this sugar to a galβ1 → 3galNAcα1 → R structure. The enzyme capable of adding NANA to galβ1 → 4glcNAcβ1 → R structures has a pH optimum of 5.5, a temperature optimum of 30 °C, and half-saturating values of 17 μM for CMP-NANA and 180 μM for galactoside termini on desialyzed α1-acid glycoprotein. It is activated about 10-fold by Triton X-100, has no exogenous divalent cation requirement, and is inhibited by CTP, CDP, and CMP. The enzyme requires carbohydrate structures underlying the galβ1 → 4glcNAc terminus for maximal catalytic activity; the necessity of such precise specificities of sialyltransferases is discussed in the light of recent structural evidence for the carbohydrate moieties of several glycoproteins.

Dibutyryl cAMP-induced Increases in triacylglycerol lipase activity in developing L8 myotube cultures

1990 ◽  
Vol 68 (6) ◽  
pp. 689-693 ◽  
Author(s):  
Warren K. Palmer ◽  
Lawrence B. Oscai ◽  
Peter J. Bechtel ◽  
Glenn A. Fisher
Keyword(s):  
Enzyme Activity ◽  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Culture Medium ◽  
Cultured Cells ◽  
Muscle Cells ◽  
Cell Types ◽  
Dibutyryl Camp ◽  
Ph Optimum ◽  
Triacylglycerol Lipase

Triacylglycerol (TG) lipase activity, with an alkaline pH optimum, has been identified in the cellular fraction of L8 myotube cultures. This TG lipase activity was stimulated by serum and inhibited by NaCl and protamine sulfate. These characteristics have been classically described for lipoprotein lipase. It was possible to increase the activity of this TG lipase three- to fivefold by incubating the cells with dibutyryl cAMP Maximal enzyme activity was observed 16 h following the addition of 10–100 μM dibutyryl cAMP to the cultured cells. Enzyme activity returned to control levels 24 h after removal of the nucleotide from the culture medium. Serum-sensitive alkaline TG lipase activity was also identified in five other myotube preparations of cultured muscle cells. The highest levels of activity were found in rat skeletal muscle primary, H9, and L6 cell types. The finding that dibutyryl cAMP is an effective inducer of alkaline TG lipase activity provides us with a valuable model to investigate mechanisms regulating synthesis, compartmentalization, and transport of lipoprotein lipase in muscle.Key words: lipoprotein lipase, cultured muscle cells, enzyme induction.

The Uptake of Adenine by Isolated Human Platelet Membranes

1974 ◽  
Vol 32 (02/03) ◽  
pp. 457-464
Author(s):  
Paul C. French ◽  
Jan J. Sixma ◽  
Holm Holmsen
Keyword(s):  
Human Platelet ◽  
Facilitated Diffusion ◽  
Adenine Phosphoribosyltransferase ◽  
Ph Optimum ◽  
Intact Cells ◽  
Platelet Membranes ◽  
Group Translocation ◽  
Triton X

SummaryAdenine uptake into isolated platelet membranes had about the same Km (151 ± 21 • 9 nM) as uptake into intact cells (159 ± 21 nM) and was also competitively inhibited by papaverine and hypoxanthine. No uptake occurred at 0° and accumulated adenine was converted to AMP. AMP was not firmly bound to protein as judged by chromatography of triton X-100 solubilized membranes on Sephadex G25. The pH optimum for adenine uptake was at pH 5-5. Exogenous 5-phosphoribosyl-l-pyrophos- phate strongly stimulated uptake. These data may be explained by uptake of adenine by facilitated diffusion followed by conversion to AMP by adenine phosphoribosyltransferase but group translocation cannot be entirely excluded.

Aspects of lipid synthesis, hydrolysis, and transport studied in selected Amazon fish

1978 ◽  
Vol 56 (4) ◽  
pp. 787-792 ◽  
Author(s):  
John S. Patton ◽  
Monty S. Haswell ◽  
Thomas W. Moon
Keyword(s):  
Fatty Acid ◽  
Lipolytic Activity ◽  
Lipid Synthesis ◽  
Blood Lipid ◽  
Dietary Lipid ◽  
Indwelling Catheter ◽  
Ph Optimum ◽  
Mesenteric Fat ◽  
Fatty Acid Release ◽  
Amazon Fish

Comparative lipogenic activities offish tissue, lipolytic activity of mesenteric fat and mode of intestinal lipid release into blood were investigated in a variety of Amazon fish. Small catfish were injected intramuscularly with [1-l4C]acetate, killed at intervals, and the lipid radioactivity of 11 separate tissues determined. In 6- and 18-h fish, the heart, eyes, dark muscle, and white muscle synthesized negligible lipid relative to the other tissues. Acetone powders of Triportheus sp, mesenteric fat contained high amounts of triglyceride lipase activity (120 nmol fatty acid release-d/min per milligram protein). The activity exhibited a pH optimum of 8.0 and was not activated by albumin, bile salts, or divalent salts nor inhibited by 1 M NaCl. Characteristics of the observed activity are identical with those of mammalian pancreatic lipase. Hoplias malabaricus were fed [1-14C]oleic acid and a chronic indwelling catheter was placed in the dorsal aorta for blood sampling. Based on the distribution of radioactivity among blood lipid classes, it is suggested that dietary lipid enters fish circulatory systems both as free fatty acid and as lipoproteins.

Changes in lipase activity when using gelatinous agents

2021 ◽  
pp. 40-41
Author(s):  
Михаил Александрович Лаврухин ◽  
Алла Евгеньевна Баженова ◽  
Оксана Сергеевна Руденко ◽  
Николай Борисович Кодратьев
Keyword(s):  
Lipase Activity ◽  
Lipolytic Activity ◽  
Lipolytic Enzymes ◽  
Agar Solution ◽  
Confectionery Products

Липолитическая порча, приводящая к появлению мыльного привкуса, является браковочным признаком кондитерских изделий. Исследовано влияние студнеобразователей на активность липолитических ферментов, Растворы пектина и желатина не оказали влияния на липолитическую активность, а 1%-ный раствор агара увеличил ее на 10 %. Результаты работы способствуют повышению сохранности кондитерских изделий. Lipolytic spoilage, which leads to the appearance of a soapy taste, is a defective sign of confectionery products. The effect of gelatinous agents on the activity of lipolytic enzymes was studied, pectin and gelatin solutions did not affect the lipolytic activity, and 1 % agar solution increased by 10 %. The results of the work contribute to improving the safety of confectionery products.

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