scholarly journals The acylation of lysophosphoradylglycerocholines in guinea-pig heart mitochondria

1987 ◽  
Vol 242 (1) ◽  
pp. 171-175 ◽  
Author(s):  
G Arthur ◽  
L L Page ◽  
C L Zaborniak ◽  
P C Choy
Keyword(s):  
Guinea Pig ◽  
Fatty Acyl ◽  
Heart Mitochondria ◽  
Acyl Donor ◽  
Mitochondrial Enzyme ◽  
Microsomal Enzymes ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Equal Importance ◽  
Acyl Acceptors

The importance of the deacylation-reacylation pathway for attaining the desired fatty acid composition in microsomal phospholipids has been well established. It is not clear, however, whether this mechanism is of equal importance in mitochondria. The absence of acyltransferase activity in mammalian heart mitochondria has been reported in a number of studies. In the present study we report the presence of acyltransferase activities for lysophosphoradylglycerocholines in guinea-pig heart mitochondria. This enzyme showed properties that were considerably different from those of the microsomal enzymes. Of all the acyl-CoAs tested (C18:0, C18:1, C18:2 and C20:4) the mitochondrial enzyme utilized only linoleoyl-CoA as fatty acyl donor and utilized both 1-acyl-sn-glycero-3-phosphocholine and 1-alkenyl-sn-glycero-3-phosphocholine as fatty acyl acceptors. The presence of significant quantities of fatty acids other than linoleate at the C-2 position of mitochondrial acylglycerophosphocholines, coupled with the specificity of the enzyme for linoleoyl-CoA, suggest that, in addition to reacylation, other mechanisms play a significant role in producing the molecular composition of these phospholipids found in the mitochondria.

The presence of 1-radyl-glycerophosphoethanolamine acyltransferase activity in guinea pig heart mitochondria

1987 ◽  
Vol 65 (12) ◽  
pp. 1016-1021 ◽  
Author(s):  
Gilbert Arthur ◽  
Cheryl L. Zaborniak ◽  
Patrick C. Choy
Keyword(s):  
Arachidonic Acid ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Guinea Pig ◽  
Acid Composition ◽  
Heart Mitochondria ◽  
Cardiac Mitochondria ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Ethanolamine Glycerophospholipids

Ethanolamine glycerophospholipids of mammalian heart mitochondria have a high content of arachidonic acid. Since the presence of acyltransferases that acylate 1-radyl glycerophosphoethanolamine had not been reported in the organelle, it was not known whether this high arachidonate content could be attained by the deacylation–reacylation pathway. In this study we have detected the presence of acyl-CoA:1-acyl-glycerophosphoethanolamine acyltransferase and acyl-CoA:1-alkenyl-glycerophosphoethanolamine acyltransferase activities in the guinea pig heart mitochondria. Both acyltransferases were active with palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, and arachidonoyl-CoAs, but the highest activities were obtained with arachidonoyl-CoA. The acyl-CoA specificities of the enzyme(s) did not reflect the fatty acid composition of the ethanolamine glycerophospholipids. The utilization of arachidonoyl-CoA by these acyltransferases in the guinea pig heart mitochondria suggests that these enzymes may play a significant role in contributing to the high arachidonate content of the ethanolamine glycerophospholipids. However, mechanisms beyond the acyl specificity of the reacylation reactions are also involved in the maintenance of the overall acyl composition of the ethanolamine glycerophospholipid in the cardiac mitochondria.

scholarly journals A new assay procedure for monoglyceride acyltransferase

1974 ◽  
Vol 141 (2) ◽  
pp. 407-411 ◽  
Author(s):  
Verena J. Short ◽  
David N. Brindley ◽  
Raymond Dils
Keyword(s):  
Enzyme Activity ◽  
Guinea Pig ◽  
Intestinal Mucosa ◽  
Microsomal Fraction ◽  
Assay System ◽  
Acyltransferase Activity ◽  
Palmitoyl Carnitine ◽  
Assay Procedure ◽  
Acyl Acceptors

1. A new assay system is described for monoglyceride acyltransferase (acylglycerol palmitoyltransferase, EC 2.3.1.22) in which palmitoyl-CoA is generated from palmitoyl-(-)-carnitine. 2. With the microsomal fraction from homogenates of guinea-pig intestinal mucosa, the Vmax. of this enzyme decreased with different acyl acceptors in the order 2-monopalmitoylglycerol>2-hexadecylglycerol>rac-1-monopalmitoylglycerol. 3. There were highly significant correlations between the monoglyceride acyltransferase activity as measured with these three substrates. This demonstrates that each of these substrates can be used to measure the same enzyme activity. 4. The advantages of using generated palmitoyl-CoA with 2-hexadecylglycerol and rac-1-monopalmitoylglycerol as model substrates for this enzyme are discussed.

Hydrolysis of 2-acyl-sn-glycero-3-phosphocholines in guinea pig heart mitochondria

1990 ◽  
Vol 68 (9) ◽  
pp. 1090-1095
Author(s):  
Ketan Badiani ◽  
Leona Page ◽  
Gilbert Arthur
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Molecular Species ◽  
Unsaturated Fatty Acids ◽  
Heart Mitochondria ◽  
Molar Ratio ◽  
Guinea Pig Heart ◽  
Rate Of Hydrolysis ◽  
The Individual ◽  
Hydrolysis Of

Although both 2-acyl-sn-glycero-3-phosphocholine and 1-acyl-sn-glycero-3-phosphocholine may be produced from phosphatidylcholine hydrolysis, studies on the former have lagged behind that of the latter. In this study a lysophospholipase A2 that hydrolyses 2-acyl-sn-glycero-3-phosphocholine has been characterized in guinea pig heart mitochondria. The lysophospholipase A2 activity was not dependent on Ca2+ and was inhibited differentially by saturated and unsaturated fatty acids. This lysophospholipase A2 activity was able to discriminate among different molecular species of 2-acyl-sn-glycero-3-phosphocholines when they were presented individually or in pairs. The order of decreasing rates of hydrolysis of different molecular species of 2-lysophosphatidylcholines, when the substrates were presented singly, was 18:2 > 20:4 > 18:1 > 16:0. A differential inhibition of the rate of hydrolysis of the individual substrates was observed when the substrates were presented in pairs. The degree of inhibition was dependent on the molar ratio of the mixed substrates. The characteristics of the enzyme suggest that involvement in the selective release of fatty acids from mitochondrial phosphatidylcholine would depend on a high selectivity of phospholipase A1 for different molecular species of phosphatidylcholine. A lysophospholipase A1 activity was also characterized in the mitochondria with a distinct acyl specificity from the lysophospholipase A2. Other characteristics of the two lysophospholipases suggest that the two reactions are not catalysed by the same enzyme.Key words: lysophospholipases, mitochondria, fatty acid relase, heart.

scholarly journals Acylation of 1-alkenyl-glycerophosphocholine and 1-acyl-glycerophosphocholine in guinea pig heart

1986 ◽  
Vol 236 (2) ◽  
pp. 481-487 ◽  
Author(s):  
G Arthur ◽  
P C Choy
Keyword(s):  
Heat Treatment ◽  
Guinea Pig ◽  
Strong Evidence ◽  
Microsomal Fraction ◽  
Kinetic Studies ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Unsaturated Acyl ◽  
Important Pathway ◽  
High Degree

The deacylation-reacylation process has been shown to be an important pathway for phospholipids to attain the desired acyl groups at the C-2 position. The acylation of 1-acyl-glycerophosphocholine (-GPC) in mammalian hearts has been well documented, but the acylation of 1-alkenyl-GPC has not been described. In this paper, we demonstrate the presence of acyl-CoA: 1-alkenyl-GPC acyltransferase for the acylation of 1-alkenyl-GPC in mammalian hearts; the highest activity is found in guinea pig heart. The guinea pig heart 1-alkenyl-GPC acyltransferase has only 10-40% of the 1-acyl-GPC acyltransferase activity, and both activities are located in the microsomal fraction. However, these two enzymes respond differently to cations, detergents and heat treatment, and the two enzymes also display different acyl specificity. Kinetic studies indicate that both reactions could not be accommodated by the same catalytic site. The results provide strong evidence that the two activities are from separate and distinct proteins. The specificity of 1-alkenyl-GPC acyltransferase for unsaturated species of acyl-CoA may play an important role in the maintenance of the high degree of unsaturated acyl groups found in guinea pig heart plasmalogens.

The uptake of 45Ca by individual phospholipids isolated from guinea pig heart mitochondria and the effect of various drugs

1970 ◽  
Vol 10 (3) ◽  
pp. 328-332 ◽  
Author(s):  
F. Piccinini ◽  
I. Galatulas ◽  
C. Galli ◽  
P. Pomarelli ◽  
D. Cova
Keyword(s):  
Guinea Pig ◽  
Heart Mitochondria ◽  
Guinea Pig Heart

Citrate Transport in Guinea Pig Heart Mitochondria

1975 ◽  
Vol 53 (5) ◽  
pp. 643-647 ◽  
Author(s):  
B. H. Robinson ◽  
J. Oei
Keyword(s):  
Guinea Pig ◽  
Liver Mitochondria ◽  
Heart Mitochondria ◽  
Glycolytic Flux ◽  
Guinea Pig Heart ◽  
Citrate Transport

Guinea pig heart mitochondria loaded with [14C]citrate show exchanges of radioactivity at 30 °C with added citrate, L-malate and phosphoenolpyruvate. These exchanges are inhibited by benzene-1,2,3-tricarboxylate.Measurements of rates of citrate transport indicate that the activity of this transporting system is low in heart mitochondria compared to that observed in liver mitochondria. The Km values obtained indicate a similarity to those obtained in liver. Citrate oxidation by coupled mitochondria was also found to be slow at 30 °C but was inhibited by benzene-1,2,3-tricarboxylate. The role of mitochondrial citrate transport in control of glycolytic flux in the heart is discussed.

Incorporation of a Voltage Sensitive Pore from Guinea Pig Heart Mitochondria into Black Lipid Membranes and Characterization of Electrical Properties

1983 ◽  
Vol 38 (7-8) ◽  
pp. 664-667 ◽  
Author(s):  
W. Schreibmayer ◽  
H. Hagauer ◽  
H. A. Tritthart
Keyword(s):  
Electrical Properties ◽  
Guinea Pig ◽  
Lipid Membranes ◽  
Heart Mitochondria ◽  
Guinea Pig Heart ◽  
Black Lipid Membranes

Abstract A pore from guinea pig heart mitochondria has been incorporated into BLM's (Black lipid membranes) in a highly oriented manner and its electrical properties studied. The pore shows multistate behaviour, the distribution of the pore between different conducting states being very sensitive to voltage. This has been proven by computation of single-pore experiments. Highest single pore conductance was 4.5 nSi in 1 ᴍ KCl, independent of voltage and with no detectable preference for cations or anions. The pore from guinea pig heart mitochondria reacts more sensitivly to voltage than pores of mitochondria from other tissues so far incorporated into BLM's.

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