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.

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 Lysophospholipase A2 activity in guinea-pig heart microsomal fractions displaying high activities with 2-acylglycerophosphocholines with linoleic and arachidonic acids

1989 ◽  
Vol 261 (2) ◽  
pp. 581-586 ◽  
Author(s):  
G Arthur
Keyword(s):  
Guinea Pig ◽  
Phospholipase A1 ◽  
Guinea Pig Heart ◽  
Mammalian Tissues ◽  
Rate Of Hydrolysis ◽  
The One ◽  
Arachidonic Acids ◽  
High Degree ◽  
Hydrolysis Of ◽  
Lysophospholipase Activity

Lysophospholipases A1 which catalyse the hydrolysis of acyl groups from 1-acylglycerophosphocholine (GPC) have been characterized in a number of mammalian tissues and do not exhibit any acyl specificity. In the present study lysophospholipase activity in guinea-pig heart microsomes (microsomal fractions) that hydrolyses 2-acyl-GPC was detected and characterized. The enzyme showed a high degree of acyl specificity. The relative rates of hydrolysis of individual 2-acyl-GPCs with different fatty acids was as follows: C18:2/C20:1/C18:1/C16:0, 14:6:1:1. When substrates were presented in pairs, the hydrolysis of each substrate by the enzyme was inhibited, but to very different extents. Of each pair of lysolipids examined (2-arachidonoyl- and 2-palmitoyl-GPC; 2-arachidonoyl- and 2-linoleoyl-GPC), the one with the expected higher rate of hydrolysis was more severely inhibited and the degree of inhibition was dependent on the concentration of the other lysolipid. The characteristics of the lysophospholipase A2 suggest the enzyme could work in concert with phospholipase A1 to release arachidonic and linoeic acids for further metabolism. The properties of lysophospholipase A2 and A1 suggest that they are different enzymes.

scholarly journals Evidence for receptor and G-protein regulation of a phosphatidylethanolamine-hydrolysing phospholipase A1 in guinea-pig heart microsomes: stimulation of phospholipase A1 activity by DL-isoprenaline and guanine nucleotides

1995 ◽  
Vol 312 (3) ◽  
pp. 805-809 ◽  
Author(s):  
K Badiani ◽  
G Arthur
Keyword(s):  
Guinea Pig ◽  
Hydrolytic Activity ◽  
Receptor Activation ◽  
Phospholipase A1 ◽  
Guinea Pig Heart ◽  
Phospholipases A2 ◽  
Adrenergic Antagonist ◽  
Beta 2 ◽  
Hydrolysis Of ◽  
Stimulation Of

While evidence has been presented for the receptor-mediated activation of phospholipases A2, C and D, the activation of phospholipase A1 subsequent to receptor activation has not been established. Phospholipase A1-catalysed hydrolysis of 1-palmitoyl-2-linoleoyl-glycerophosphoethanolamine (GPE) by guinea-pig heart microsomes was stimulated 40-60% by isoprenaline. This isoprenaline-mediated increase in activity was blocked by propranolol and butoxamine, a specific beta 2-adrenergic antagonist, but not by atenolol, a specific beta 1-adrenergic antagonist. Neither clonidine nor phenylephrine, alpha 1- and alpha 2-adrenergic agonists respectively, had a stimulatory effect on the hydrolysis of the PE substrate. Guanosine 5′(-)[gamma-thio]triphosphate (GTP[S]) and guanosine 5′(-)[beta, gamma-imido]triphosphate, but not guanosine 5′(-)[beta-thio]diphosphate (GDP[S]) or adenosine 5′(-)[gamma-thio]triphosphate, stimulated the hydrolysis of 1-palmitoyl-2-linoleoyl-GPE by phospholipase A1. GDP[S] inhibited the isoprenaline-mediated stimulation of phospholipase A1 activity. Phospholipase A1 hydrolysis of 1-palmitoyl-2-linoleoyl-GPE was not dependent on cations; however, the stimulatory effects of isoprenaline and GTP[S] on the hydrolytic activity were abolished by cation chelators. The above data suggest that phospholipase A1 activity in guinea-pig heart microsomes is activated by the binding of isoprenaline to beta 2-adrenergic receptors. Furthermore the stimulation of phospholipase A1 activity by the agonist may be mediated via activation of G-proteins.

scholarly journals Acylation of 2-acyl-glycerophosphocholine in guinea-pig heart microsomal fractions

1989 ◽  
Vol 261 (2) ◽  
pp. 575-580 ◽  
Author(s):  
G Arthur
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Guinea Pig ◽  
Cardiac Tissue ◽  
Saturated Fatty Acids ◽  
Asymmetric Distribution ◽  
Guinea Pig Heart ◽  
Coa Hydrolase

Acyl-CoA:2-acyl-sn-glycero-3-phosphocholine (GPC) acyltransferase is required for the maintenance of the asymmetric distribution of saturated fatty acids at the C-1 position of phosphatidylcholine; however, this activity has been reported to be absent in cardiac tissue. In the present study a very active acyl-CoA:2-acyl-GPC activity was detected and characterized in guinea-pig heart microsomes (microsomal fractions); the mitochondria did not appear to possess this activity. The acyl-CoA specificity of the microsomal acyl-CoA:2-acyl-GPC acyltransferase was distinct from the corresponding acyl-CoA:1-acyl-GPC acyltransferase. These differences were due to the position of the fatty acid on the lysophospholipid rather than the composition of the fatty acids. The enzyme did not exhibit a distinct preference for saturated fatty acids, as might be expected. Our results suggest that, in the heart, control of the intracellular composition and concentration of acyl-CoAs by acyl-CoA hydrolase and acyl-CoA synthetase may play an important role in maintaining the asymmetric distribution of fatty acids in phosphatidylcholine.

scholarly journals A rapid direct assay for the determination of the separate activities of the three arylsulphatases of Aspergillus oryzae

1977 ◽  
Vol 166 (3) ◽  
pp. 411-413 ◽  
Author(s):  
G R J Burns ◽  
C H Wynn
Keyword(s):  
Phenolic Compounds ◽  
Aspergillus Oryzae ◽  
Substrate Specificities ◽  
Direct Assay ◽  
Assay Procedure ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Potential Use

1. The three arylsulphatases of Aspergillus oryzae exhibit pronounced kinetic differences and substrate specificities. Arylsulphatase I hydrolyses all substrates tested, whereas arylsulphatase III will not hydrolyse tyrosine O-sulphate or phenolphthalein disulphate. Arylsulphatase II does not hydrolyse p-nitrophenyl sulphate or phenolphthalein disulphate at appreciable rates in the absence of added phenolic compounds. Phenols such as tyramine increase the rate of hydrolysis of these substances by this enzyme 1000-fold. At pH 6.9 arylsulphatase I exhibits an apparent Km of 0.1 mM for p-nitrophenyl sulphate, whereas the Km of arylsulphatase III for this substrate is 1 mM. 2. These differences were utilized to develop an assay procedure which can be used to determine the separate activities of the three enzymes present in mixtures. This assay has potential use as a means of examining the relative activities of the three enzymes in investigations of the differences in the mechanisms regulating their synthesis.

Rapid in vivo hydrolysis of fatty acid ethyl esters, toxic nonoxidative ethanol metabolites

1997 ◽  
Vol 273 (1) ◽  
pp. G184-G190 ◽  
Author(s):  
M. Saghir ◽  
J. Werner ◽  
M. Laposata
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Free Fatty Acids ◽  
Fatty Acid Ethyl Esters ◽  
Ethyl Esters ◽  
Ethanol Ingestion ◽  
Gi Tract ◽  
Apparent Lack ◽  
Hydrolysis Of

Fatty acid ethyl esters (FAEE), esterification products of fatty acids and ethanol, are in use as fatty acid supplements, but they also have been implicated as toxic mediators of ethanol ingestion. We hypothesized that hydrolysis of orally ingested FAEE occurs in the gastrointestinal (GI) tract and in the blood to explain their apparent lack of toxicity. To study the in vivo inactivation of FAEE by hydrolysis to free fatty acids and ethanol, we assessed the hydrolysis of FAEE administered as an oil directly into the rat stomach and when injected within the core of low-density lipoprotein particles into the circulation of rats. Our studies demonstrate that FAEE are rapidly degraded to free fatty acids and ethanol in the GI tract at the level of the duodenum with limited hydrolysis in the stomach. In addition, FAEE are rapidly degraded in the circulation, with a half-life of only 58 s. Thus the degradation of FAEE in the GI tract and in the blood provides an explanation for the apparent lack of toxicity of orally ingested FAEE.

Lipids of the fin whale (Balaenoptera physalus) from North Atlantic waters. IV. Fin whale milk

1968 ◽  
Vol 46 (3) ◽  
pp. 197-203 ◽  
Author(s):  
R. G. Ackman ◽  
C. A. Eaton ◽  
S. N. Hooper
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Polyunsaturated Fatty Acids ◽  
Total Lipid ◽  
Iodine Value ◽  
North Atlantic ◽  
Methyl Esters ◽  
Short Chain Fatty Acids ◽  
Fin Whale ◽  
Hydrolysis Of

Fatty acid compositions were determined for total lipid (17.5% of the milk and > 95% triglycerides), 2-monoglyceride obtained by enzymatic hydrolysis of isolated triglyceride, and isolated phospholipid (~1% of total lipids). The total lipid fatty acids of the milk had a composition similar to fin whale depot fat but were enriched in hexadecanoic acid and polyunsaturated fatty acids at the expense of monoethylenic acids; correspondingly the iodine value of 136 (methyl esters) was higher than the normal range (105–120) of North Atlantic fin whale blubber oils. Over 80% of the fatty acids in the 2-position of the triglycerides were accounted for by relatively short chain fatty acids, especially hexadecanoic (54.6%), tetradecanoic (13.7%), and hexadecenoic (11.2%), so that the ester iodine value was only 48. The milk phospholipids had a fatty acid composition basically similar to that of liver phospholipids (methyl ester iodine value 120) with somewhat more polyunsaturated fatty acids and accordingly an iodine value of 144 for methyl esters.

Hydrocortisone inhibits mucin secretion from guinea pig gallbladder

1984 ◽  
Vol 247 (4) ◽  
pp. G427-G431 ◽  
Author(s):  
J. R. Moore ◽  
B. S. Turner ◽  
J. T. LaMont
Keyword(s):  
Guinea Pig ◽  
Phospholipase A2 ◽  
Sodium Succinate ◽  
Inhibitory Effect ◽  
Membrane Phospholipids ◽  
Mucin Secretion ◽  
Basal Secretion ◽  
Prostaglandin Release ◽  
Hydrolysis Of

We studied the effects of hydrocortisone, an inhibitor of phospholipase A2, on the secretion of mucin and release of prostaglandins from guinea pig gallbladder explants. We measured mucin using [3H]glucosamine as a precursor and prostaglandins by radioimmunoassay of 6-keto-prostaglandin F1 alpha. Mucin secretion and prostaglandin release were studied under basal conditions and after arachidonate stimulation. Hydrocortisone sodium succinate reversibly inhibited basal secretion of mucin by 24% at 10(-5) M (P less than 0.05 compared with control) and 34% at 10(-4) M (P less than 0.01). Hydrocortisone, 10(-4) M, also reversibly inhibited arachidonate-stimulated secretion of mucin (P less than 0.01 compared with controls incubated with arachidonate alone). Release of prostaglandin F1 alpha was significantly inhibited by hydrocortisone under basal (P less than 0.01) and arachidonate-stimulated (P less than 0.01) conditions. The inhibitory effect of hydrocortisone was mediated by inhibition of hydrolysis of arachidonate from membrane phospholipids, suggesting that exogenous arachidonate is incorporated into membrane phospholipids prior to conversion to prostaglandins.

scholarly journals Characterization of the oils present in acid and fermented silages produced from Tilapia filleting residue

2011 ◽  
Vol 40 (2) ◽  
pp. 240-244 ◽  
Author(s):  
Rose Meire Vidotti ◽  
Maria Teresa Bertoldo Pacheco ◽  
Giovani Sampaio Gonçalves
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Nutritional Value ◽  
Lipid Fraction ◽  
Monounsaturated Fatty Acids ◽  
Degree Of Saturation ◽  
Degree Of Hydrolysis ◽  
Animal Feeding ◽  
Hydrolysis Of

The objective of this study was to determine the quality and composition of fatty acid in the lipid fraction of silages obtained from the residue of tilapia processing. Stratification of the lipid layer of the silages occurred at different times among the two types of silage (acid and fermented) and the greatest volume of oil was observed in acid silage (8.67% p/p). Although acid silage was more oxidized, it showed lower contents of free fatty acids probably because the degree of hydrolysis of its components is lower than that of fermented silage. Fatty acid composition did not differ among processes inasmuch as level of ϖ-3 was slightly higher in fermented silage. According to the degree of saturation, monounsaturated fatty acids stood out as the predominant category in acid and fermented silages with values of 39.69% and 33.39%, respectively. The use of antioxidants in the silage is needed because the process of production is carried out at temperatures higher than room temperature. The oil in the silages has excellent nutritional value and contains fatty acids essential for animal feeding.

Evidence that fatty acid chain length is a type II cell lipid-sorting signal

1991 ◽  
Vol 260 (2) ◽  
pp. L44-L51 ◽  
Author(s):  
K. J. Longmuir ◽  
S. Haynes
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Chain Length ◽  
Molecular Species ◽  
Palmitoleic Acid ◽  
Lamellar Body ◽  
Structural Features ◽  
Type Ii ◽  
Fatty Acid Chain ◽  
Type Ii Cell

This study was undertaken to determine those structural features of phospholipid molecules which influence their enrichment in type II cell lamellar body material. Cultured fetal rabbit lung tissue was labeled with [1-14C]acetate, type II cells were isolated, and extracellular lamellar body and microsomal fractions were prepared. Radiolabeled molecular species of phosphatidylcholine (PC) and phosphatidylethanolamine were analyzed by high-performance liquid chromatography (HPLC), followed by silver nitrate thin-layer chromatography of HPLC peak fractions that overlapped. Compared with microsomes, lamellar body PC was selectively enriched with molecular species containing 14- and 16-carbon fatty acids and depleted of species containing 18-carbon fatty acids. Palmitoleic acid and an ether linkage positively influenced the enrichment of PC molecular species in the lamellar body material, but these structural features were secondary to the predominant influence of fatty acid chain length. In vivo, lung tissue normally contains low levels of palmitoleic acid; hence most unsaturated fatty acids are 18-carbons or longer. A cellular lipid-sorting mechanism that selects PCs by recognition of 14- and 16-carbon fatty acid chains (and not by recognition of fatty acid saturation) should serve to enrich the resulting pulmonary surfactant with disaturated molecular species of PC.

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