The biosynthesis of phosphatidylcholine molecular species in fetal and neonatal guinea pig lung

1991 ◽  
Vol 19 (2) ◽  
pp. 112S-112S ◽  
Author(s):  
GRAHAM C. BURDGE ◽  
FRANK J. KELLY ◽  
ANTHONY D. POSTLE
Keyword(s):  
Guinea Pig ◽  
Molecular Species

scholarly journals Evidence for the regulation of guinea-pig heart microsomal phosphatidylcholine-hydrolysing phospholipase A1 by guanosine 5′-[γ-thio]triphosphate

1992 ◽  
Vol 288 (3) ◽  
pp. 965-968 ◽  
Author(s):  
K Badiani ◽  
X Lu ◽  
G Arthur
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Guinea Pig ◽  
Molecular Species ◽  
Inhibitory Effect ◽  
Phospholipase A1 ◽  
Guinea Pig Heart ◽  
Substrate Specificities ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

We have recently characterized lysophospholipase A2 activities in guinea-pig heart microsomes and postulated that these enzymes act sequentially with phospholipases A1 to release fatty acids selectively from phosphatidylcholine (PC) and phosphatidylethanolamine, thus providing an alternative route to the phospholipase A2 mode of release. In a further investigation of the postulated pathway, we have characterized the PC-hydrolysing phospholipase A1 in guinea-pig heart microsomes. Our results show that the enzyme may have a preference for substrates with C16:0 over C18:0 at the sn-1 position. In addition, although the enzyme cleaves the sn-1 fatty acid, the rate of hydrolysis of PC substrates with C16:0 at the sn-1 position was influenced by the nature of the fatty acid at the sn-2 position. The order of decreasing preference was C18:2 > C20:4 = C18:1 > C16:0. The hydrolyses of the molecular species were differentially affected by heating at 60 degrees C. An investigation into the effect of nucleotides on the activity of the enzyme showed that guanosine 5′-[gamma-thio]triphosphate (GTP[S]) inhibited the hydrolysis of PC by phospholipase A1 activity, whereas GTP, guanosine 5′-[beta-thio]diphosphate (GDP[S]), GDP, ATP and adenosine 5′-[gamma-thio]triphosphate (ATP[S]) did not affect the activity. The inhibitory effect of GTP[S] on phospholipase A1 activity was blocked by preincubation with GDP[S]. A differential effect of GTP[S] on the hydrolysis of different molecular species was also observed. Taken together, the results of this study suggest the presence of more than one phospholipase A1 in the microsomes with different substrate specificities, which act sequentially with lysophospholipase A2 to release linoleic or arachidonic acid selectively from PC under resting conditions. Upon stimulation and activation of the G-protein, the release of fatty acids would be inhibited.

Hepatic phospholipid molecular species in the guinea pig adaptations to pregnancy

Lipids ◽  
1994 ◽  
Vol 29 (4) ◽  
pp. 259-264 ◽  
Author(s):  
Graham C. Burdge ◽  
Anthony D. Postle
Keyword(s):  
Guinea Pig ◽  
Molecular Species ◽  
Phospholipid Molecular Species

scholarly journals Mechanisms of hepatic phosphatidylcholine synthesis in the developing guinea pig: contributions of acyl remodelling and of N-methylation of phosphatidylethanolamine

1993 ◽  
Vol 290 (1) ◽  
pp. 67-73 ◽  
Author(s):  
G C Burdge ◽  
F J Kelly ◽  
A D Postle
Keyword(s):  
Fatty Acids ◽  
Guinea Pig ◽  
Molecular Species ◽  
Essential Fatty Acids ◽  
Specific Radioactivity ◽  
Long Chain Fatty Acids ◽  
Radioactivity Analysis ◽  
Species Specific ◽  
Phosphatidylcholine Synthesis

Hepatic phosphatidylcholine (PC) from the immature fetal guinea pig at day 55 of gestation comprised mainly unsaturated molecular species containing C18:2(n-6) and C22:6(n-3) at the sn-2 position, reflecting placental permeability to essential fatty acids. At both day 55 and term (day 68), [Me-14C]choline was incorporated in utero over 3 h largely into sn-1-C16:0 PC species, with incorporation into sn-1-C18:0 PC species increasing by 18 h of incubation. Comparison of specific radioactivities after 3 h and 18 h suggests PC acyl remodelling by phospholipase A1. No incorporation into C20:4(n-6)-containing PC species could be detected of either [Me-14C]choline in vivo or CDP-[Me-14C]choline in isolated microsomes. The major phosphatidylethanolamine (PE) species were 16:0/22:6 and 18:0/22:6. Although [14C]ethanolamine was initially incorporated mainly into sn-1-C16:0 species, specific-radioactivity analysis suggested differential turnover rather than acyl remodelling. [1,2-14C]Ethanolamine and [Me-14C]methionine incorporation into PC molecular species indicated that both newly synthesized and total PE pools were available for N-methylation. Since the PC pool synthesized from PE included C20:4- and C22:6-containing species, N-methylation may provide a mechanism for supplying essential long-chain fatty acids to developing tissues that can be regulated independently from bulk PC synthesis.

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.

The biosynthesis of molecular species of phosphatidylcholine in neonatal guinea pig liver

1991 ◽  
Vol 19 (2) ◽  
pp. 113S-113S
Author(s):  
GRAHAM C. BURDGE ◽  
FRANK J. KELLY ◽  
ANTHONY D. POSTLE
Keyword(s):  
Guinea Pig ◽  
Molecular Species ◽  
Pig Liver ◽  
Guinea Pig Liver
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