Lipid involvement in oleoyl CoA desaturase activity of Fusarium oxysporum microsomes

Desaturation of oleoyl CoA by the microsomal fraction of Fusarium oxysporum hyphal cells required O2, NADPH, MgCl2, and the addition of either bovine serum albumin or the 105 000g supernatant fraction. In the absence of reduced nucleotide, [14C]oleoyl CoA was rapidly incorporated into phospholipid and triacylglycerol and hydrolyzed to free fatty acids. After addition of NADPH, oleate was desaturated at the normal rate. Analysis of the distribution of [14C]oleate and [14C]linoleate between different lipid classes revealed that phosphatidylcholine and phosphatidylethanolamine were labeled with [14C]linoleate before any other lipid class. These results are consistent with oleoyl phospholipid being a direct intermediate in the desaturation of oleoyl CoA. The preference of the oleoyl-desaturase for NADPH, the relatively high pH optimum of 8.2, and the sensitivity to thenoyltrifluoroacetone inhibition suggest that some components of the microsomal electron-transport chain are common to both the oleoyl desaturase and stearoyl CoA desaturase systems in this fungus.     

Activation of bee venom phospholipase A2 by oleoyl imidazolide produces a thiol- and proteinase-resistant conformation

Assay methods for bee venom phospholipase A2 are presented which respond to different aspects of enzymic behaviour and which allow basal activity, fatty acid activation and acyl-group activation to be distinguished. The stability of the enzyme to thiols and proteinases is dramatically increased by activation with the selective acylating agent, oleoyl imidazolide. These results support the model of activation by conformation change. Limited-fixation studies indicate that enzyme conformation is determined by interaction with the substrate. The oleoyl-enzyme is partially inactivated by trypsin, but its electrophoretic mobility is unchanged. This protective effect is highly selective and only one other component of the venom is protected against trypsin by oleoyl imidazolide. Combination of trypsin and thiol treatment produces a large fragment of the activated enzyme which could be used for structural studies of the activation site.     

Modification of lysozyme with oleoyl chloride for broadening the antimicrobial specificity

Lysozyme from egg white was modified by covalent attachment of an oleyl group to the free amino groups of lysozyme. The aim of the chemical modification was to develop an effective antimicrobial lysozyme derivative against both gram-negative and gram-positive bacteria. Lysozyme with various degrees of modification was obtained by changing oleoyl chloride/lysozyme mass ratio. Lysozyme derivatives evidently exhibited an antimicrobial effect against Escherichia coli (ATCC 29998). The modification slightly changed the antimicrobial effect of lysozyme derivative against Staphylococcus aureus (ATCC 121002). Since there was a positive correlation between the modification degree and the antimicrobial effect against E. coli, it was concluded that the change in antimicrobial behavior was due to an increase in hydrophobicity of the enzyme molecule enabling it to penetrate through the bacterial membrane of E. coli. It was also shown that oleoyl chloride with an MIC value of 10?mg/mL was effective against both E. coli and S. aureus.     

Activation of the acidic isoform of phospholipase A2 from Naja mossambica mossambica venom by oleoyl imidazolide requires the cooperative action of two ionizing groups

The acidic phospholipase A2 isoform from the spitting cobra Naja mossambica mossambica is activated irreversibly by treatment with a molar equivalent of oleoyl imidazolide. The kinetics of the chemical modification of the enzyme can also be monitored by measuring the large reduction of tryptophan fluorescence, which is accompanied by a distinct red shift. The addition of a single molar equivalent of oleic acid to the enzyme produces an instantaneous reduction in fluorescence but with a barely detectable red shift, confirming that the response to oleoyl imidazolide results from covalent modification of the protein rather than hydrolysis of the reagent. The pH dependence of both activation and fluorescence reduction by oleoyl imidazolide has an optimum rate near pH 8.0. We propose that long-chain fatty acids and long-chain acyl imidazolides bind at a single activation site and that the reaction of the imidazolides involves two protein residues, one of which is a nonessential histidine residue and the other a primary amino group.     

Evidence for an oleoyl phosphatidylcholine desaturase in microsomal preparations from cotyledons of safflower (Carthamus tinctorius) seed.

1. [14C]Oleoyl-CoA was metabolized rapidly and essentially completely by microsomal preparations from developing safflower (Carthamus tinctorius) cotyledons, and most of the [14C]oleate was incorporated into 3-sn-phosphatidylcholine. 2. In aerobic reaction mixtures containing NADH2 the [14C]oleate in 3-sn-phosphatidylcholine was converted into [14C]linoleate without any change in the specific radioactivity of the lipid. Over a 60 min incubation period the extent of conversion of [14C]oleoyl phosphatidylcholine into [14C]linoleoyl phosphatidylcholine was generally greater than 60%. The rate of desaturation of endogenous [14C]oleoyl phosphatidylcholine labelled from [14C]oleoyl-CoA was much greater that of exogenous [14C]dioleoyl phosphatidylcholine the specific radioactivity of the oleoyl moiety of the lipid remained constant, indicating that labelled and unlabelled oleate were desaturated at the same rate. On this assumption an initial rate of desaturation of about 15 nmol of oleate desaturated/min per mumol of 3-sn-phosphatidylcholine was estimated. 4. [14C]Oleate esterified at positions 1 and 2 of both endogenous and exogenous 3-sn-phosphatidylcholine was desaturated. 5. Attempts to demonstrate the presence of an oleoyl-CoA desaturase in safflower microsomal fractions by the appearance of linoleoyl-CoA in reaction mixtures were inconclusive.     

Solubilisation of oleoyl-CoA thioesterase,oleoyl-CoA: phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase: The oleate desaturase system of pea leaf microsomes

Membrane-bound enzymes involved in oleate metabolism in microsomes from pea (Pisum sativum L.) leaves were solubilised using detergents, such as n-octyl glucoside, Triton X-100, digitonin or cholate. The detergents were found to be inhibitory to oleoyl-CoA thioesterase, oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. Detergent removal by dialysis resulted in the restoration of activity of both the solubilised oleoyl-CoA thioesterase and oleoyl-CoA:phosphatidylcholine acyltransferase. The putative components of the oleoyl phosphatidylcholine desaturase system were also partially solubilised.     

Interaction of apolipoprotein A-I in three different conformations with palmitoyl oleoyl phosphatidylcholine vesicles

Interactions of apolipoprotein A-I (apoA-I) with cell membranes appear to be important in the initial steps of reverse cholesterol transport. The objective of this work was to examine the effect of three distinct conformations of apoA-I (lipid-free and in 78 A or 96 A reconstituted high density lipoproteins, rHDL) on its ability to bind to, and abstract lipids from, palmitoyl oleoyl phosphatidylcholine membrane vesicles (small unilamellar vesicles, SUV, and giant unilamellar vesicles, GUV). The molecular interactions were observed by two-photon fluorescence microscopy, and the binding parameters were quantified by gel-permeation chromatography or isothermal titration microcalorimetry. Rearrangement of apoA-I-containing particles after exposure to SUVs was examined by native gel electrophoresis. The results indicate that lipid-free apoA-I binds reversibly, with high affinity, to the vesicles but does not abstract a significant amount of lipid nor perturb the vesicle structure. The 96 A rHDL, where all the amphipathic helices of apoA-I are saturated with lipid within the particles, do not bind to vesicles or perturb their structure. In contrast, the 78 A rHDL have a region of apoA-I, corresponding to a few amphipathic helical segments, which is available for external or internal phospholipid binding. These particles bind to vesicles with measurable affinity (lower than lipid-free apoA-I), abstract lipids from the membranes, and form particles of larger diameters, including 96 A rHDL. We conclude that the conformation of apoA-I regulates its binding affinity for phospholipid membranes and its ability to abstract lipids from the membranes.     

Covalent binding of photosensitive 1-(12-azido-[9,10(-3)H2]oleoyl)glycero-3-phosphocholine (lysolecithin) to human serum high density apolipoproteins.

Human serum high density apoproteins were complexed with increasing concentrations of 1-(12-azido-[9,10(-3)H2]oleoyl)glycero-3-phosphocholine up to the saturation concentration (72 mol lysolecithin per mol apo HDL). Ultraviolet irradiation generated the nitrene which led to crosslinking with the two main apolipoproteins AI and AII. Methods are described for the removal of excess, unbound lipid and the column chromatographic separation of the lipopolypeptides AI and AII.     

Expression of melanoma neutral proteinase and collagenase potential by endocytosis.

When oleoyl phosphate and ADP were incubated with heart submitochondrial particles in the presence of glucose-hexokinase trap according to a reported procedure [Griffiths, D.E. (1976) Biochem. J. 160: 809–812], a 10% yield of glucose-6-phosphate was detected by chemical analysis. Although lower concentration of oleoyl phosphate improved the yield to 80–85%, the mode of formation of glucose-6-phosphate was not clear under the experimental condition used to improve the yield. In order to test decisively whether the phosphoryl group of oleoyl phosphate was transferred to ADP to form ATP which was estimated in the form of glucose-6-phosphate, [³²P]oleoyl phosphate was synthesized. The use of isotopically labelled oleoyl phosphate showed only about 5% yield of [³²P]glucose-6-phosphate by paper chromatographic analysis, whereas chemical analysis of the same system gave 80% yield of glucose-6-phosphate. Such an observation demonstrated that glucose-6-phosphate estimated by chemical assay is not the result of phosphorylation of ADP with oleoyl phosphate catalyzed by the submitochondrial particles.     

Acyl coenzyme a preference of diacylglycerol acyltransferase from the maturing seeds of cuphea, maize, rapeseed, and canola

In their seed triacylglycerols, Cuphea carthagenensis contains 62% lauric acid; maize possesses 50% linoleic acid and 30% oleic acid; rapeseed (Brassica napus L. var Dwarf Essex) has 40% erucic acid; and Canola (Brassica napus L. var Tower) holds 60% oleic acid and 23% linoleic acid. Diacylglycerol acyltransferase (EC 2.3.1.20) in the microsomal preparations from maturing seeds of the above species were tested for their preference in using different forms of acyl coenzyme A (CoA). Lauroyl CoA, oleoyl CoA, and erucoyl CoA individually or in equimolar mixtures at increasing concentrations were added to the assay mixture containing diolein, and the formation of triacylglycerols from the acyl groups at 24, 32, and 40°C was analyzed. The Cuphea enzyme preferred lauroyl CoA to oleoyl CoA, and was inactive on erucoyl CoA. The maize enzyme had about equal activities on oleoyl CoA and lauroyl CoA, and was inactive on erucoyl CoA. Enzymes from both rapeseed and Canola had the same pattern of acyl CoA preference, with highest activities on lauroyl CoA. The two enzymes were more active on oleoyl CoA than on erucoyl CoA at high acyl CoA concentrations (10 and 20 micromolar) at 24°C, but were more active on erucoyl CoA than on oleoyl CoA at low acyl CoA concentrations (1.36 micromolar or less) at 32 and 40°C. These findings are discussed in terms of the contribution of the enzyme to the acyl specificity in storage triacylglycerols and the implication in seed oil biotechnology.     

Improvement of Metabolic and Histological Changes of Adiposity in Rats by Synthetic Oleoyl Chalcones

We previously reported that synthetic oleoyl chalcones had a favorable effect to alleviate metabolic consequences of obesity in male SD rats. In this work, we prepared and characterized by spectroscopic tools, a set of six oleoyl chalcones ( 5a–c , 10 and 11a,b ). The comparative effects of the previously prepared oleoyl chalcones and their new synthetic analogs on metabolic and histological changes in obese male SD rats were studied. It was found that the oleoyl chalcones III_a and IV were the best in improving many metabolic parameters, e. g., FBG, FI, ISI, TG, and total cholesterol. They cured systemic inflammation, through inhibition of the TNF-α and induction of adiponectin production. Moreover, chalcones III_a and IV alleviated the oxidative stress accompanying obesity through the induction of the antioxidant enzymes GPX, SOD and CAT besides, GSH. Interestingly, chalcones III_a and IV exerted hepatoprotective potency and ameliorated the manifestations of NAFLD via inhibition of apoptosis and induction of autophagy of hepatic cells. In conclusion, the oleoyl chalcones III_a and IV were the most effective candidates among the series of synthetic chalcones in correcting body weight and the consequent metabolic and histological changes in adiposity.     

Comparison of rates of hydrolysis of N-oleoyl and N-stearoyl glucocerebroside in patients with Gaucher's disease

The deficiency of oleic acid as one of the fatty acids in glucocerebrosides that accumulate (31--77 mg/g dry weight) in the spleen in patients with Gaucher's disease was confirmed in 9 cases. In an effort to account for the 10-fold difference between the oleoyl glycocerebroside content of glucocerebrosides in spleen from controls and patients with Gaucher's disease, we compared the ability of extracts of spleen and fibroblasts from individuals with various forms of Gaucher's disease and controls to hydrolyze [14C]stearoyl and [3H]oleoyl glucocerebroside. The residual glucosylceramidase activity in patients with Gaucher's disease hydrolyzes the glucose moiety of oleoyl glucocerebroside at approximately the same rate as that of stearoyl glucocerebroside. Similarly, the more active glucosylceramidase of control tissue acts upon both oleoyl and stearoyl glucocerebrosides with equal efficiency. These observations indicate that a mutation affecting the substrate specificity of glucosylceramidase cannot account for the lack of oleic acid-containing glucocerebrosides in patients with Gaucher's disease. Thus, the hypothesis that the difference in fatty acid composition found in glucocerebroside is obtained as a result of a mutation affecting the specificity of the residual glucosylceramidase must be rejected.     

Phorbol esters and oleoyl acetoyl glycerol enhance release of arachidonic acid in platelets stimulated by Ca2+ ionophore A23187

Washed human platelets prelabeled with [14C]arachidonic acid and then exposed to the Ca2+ ionophore A23187 mobilized [14C]arachidonic acid from phospholipids and formed 14C-labeled thromboxane B2, 12-hydroxy-5-8,10-heptadecatrienoic acid, and 12-hydroxy-5,8,10,14-eicosatetraenoic acid. Addition of phorbol myristate acetate (PMA) by itself at concentrations from 10 to 1000 ng/ml did not release arachidonic acid or cause the formation of any of its metabolites, nor did it affect the metabolism of exogenously added arachidonic acid. When 1 microM A23187 was added to platelets pretreated with 100 ng of PMA/ml for 10 min, the release of arachidonic acid, and the amount of all arachidonic acid metabolites formed, were greatly increased (average 4.1 +/- 0.5-fold in eight experiments). This effect of PMA was mimicked by other stimulators of protein kinase C, such as phorbol dibutyrate and oleoyl acetoyl glycerol, but not by 4-alpha-phorbol 12,13-didecanoate, which does not stimulate protein kinase C. However, phosphorylation of the cytosolic 47-kDa protein, the major substrate for protein kinase C in platelets, was produced at lower concentrations of PMA and at a much higher rate than enhancement of arachidonic acid release by PMA, suggesting that 47-kDa protein phosphorylation is not directly involved in mobilization of the fatty acid. PMA also potentiated arachidonic acid release when stimulation of phospholipase C by the ionophore (which is due to thromboxane A2 and/or secreted ADP) was blocked by aspirin plus ADP scavengers, i.e. apyrase or creatine phosphate/creatine phosphokinase. Increased release of arachidonic acid was attributable to loss of [14C]arachidonic acid primarily from phosphatidylcholine (79%) with lesser amounts derived from phosphatidylinositol (12%) and phosphatidylethanolamine (8%). Phosphatidic acid, whose production is a sensitive indicator of phospholipase C activation, was not formed. Thus, the potentiation of arachidonic acid release by PMA appeared to be due to phospholipase A2 activity. These results suggest that diacylglycerol formed in response to stimulation of platelet receptors by agonists may cooperatively promote release of arachidonic acid via a Ca2+/phospholipase A2-dependent pathway.     

Lipid acyl chain-dependent effects of sterols in Acholeplasma laidlawii membranes.

Acholeplasma laidlawii was grown with different fatty acids for membrane lipid synthesis (saturated straight- and branched-chain acids and mono- and di-unsaturated acids). The ability of 12 different sterols to affect cell growth, lipid head group composition, the order parameter of the acyl chains, and the phase equilibria of in vivo lipid mixtures was studied. The following two effects were observed with respect to cell growth: with a given acyl chain composition of the membrane lipids, growth was stimulated, unaffected, reduced, or completely inhibited (lysis), depending on the sterol structure; and the effect of a certain sterol depended on the acyl chain composition (most striking for epicoprostanol, cholest-4-en-3-one, and cholest-5-en-3-one, which stimulated growth with saturated acyl chains but caused lysis with unsaturated chains). The three lytic sterols were the only sterols that caused a marked decrease in the ratio between the major lipids monoglucosyldiglyceride and diglucosyldiglyceride and hence a decrease in bilayer stability when the membranes were enriched in saturated (palmitoyl) chains. With these chains correlations were found for several sterols between the glucolipid ratio and the order parameter of the acyl chains, as well as the lamellar-reversed hexagonal phase transition, in model systems. A shaft experiment revealed a marked decrease in the ratio of monoglucosyldiglyceride to diglucosyldiglyceride with the lytic sterols in unsaturated (oleoyl) membranes. The two cholestenes induced nonlamellar phases in in vivo mixtures of oleoyl A. laidlawii lipids. The order parameters of the oleoyl chains were almost unaffected by the sterols. Generally, the observed effects cannot be explained by an influence of the sterols on the gel-to-liquid crystalline phase transition.     

Oleate metabolism in microsomes from developing leaves ofPisum sativum L.

Microsomes from young leaves of pea,Pisum sativum L., metabolized oleate principally by the reactions mediated by oleoyl-CoA synthetase, oleoyl-CoA thioesterase, oleoyl-CoA: phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. Hydrogen peroxide specifically inhibited oleate desaturation and the evidence presented argues for a specific inhibition of the terminal enzyme of the desaturase system, i.e. oleoyl phosphatidylcholine desaturase. Catalase, ascorbic acid, or ascorbate peroxidase, in conjunction with ascorbic acid, stimulated oleate desaturation, possibly by the removal of hydrogen peroxide. Lysophosphatidylcholine was found to be the preferred acceptor for acyl transfer from oleoyl-CoA, which indicates that the transfer of oleoyl moieties was catalyzed predominantly by oleoyl-CoA:lysophosphatidylcholine acyltransferase. Acyl exchange between oleoyl-CoA and phosphatidylcholine, with a possible involvement of phospholipases, was also detected but at much lower rates than acyl transfer. When intact or broken chloroplasts were added to microsomes, which had been preincubated with oleoyl-CoA, some stimulation of the reactions catalyzed by oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase was observed. However, only minor amounts of microsomal linoleoyl phosphatidylcholine were converted to galactolipids containing linolenoyl moieties.Abbreviations FA unesterified fatty acid (s) - PC phosphatidylcholines - 18:1 oleoyl moieties - 18:2 lmoleoyl moieties Dedicated to Professor Helmut K. Mangold, Bundesanstalt für Fettforschung, Münster, on his 60th birthday     

Photo-induced dimerization of anthracene phospholipids for the study of the lateral distribution of lipids in membranes

The biosynthesis of linoleic acid has been investigated, using oleoyl-CoA as a substrate, in microsomal preparations from young leaves of Pisum sativum. Oleoyl moieties from oleoyl-CoA were preferentially acylated to lysophosphatidylcholine by an acyltransferase to produce an oleoylglycerophosphocholine. Kinetic data are presented which argue for a direct desaturation of the oleoyl moieties of this oleoyl glycerophosphocholine to linoleoyl moieties. There was no evidence of a subsequent acyltransfer of linoleoyl moieties either to form thioesters or oxygen esters in other complex lipids. The kinetics were also consistent with a functional coupling of the lysophosphatidylcholine acyltransferase with the oleate desaturase. There was little exchange of the oleoyl glycerophosphocholine from the bulk membrane lipid with that newly synthesised by the lysophosphatidylcholine acyltransferase. Rather, the newly synthesised oleoylglycerophosphocholine seemed to be directly channelled to the vicinity of the desaturase. The results are discussed in the context of 'metabolite channelling'. The consequences for desaturase activity and its regulation are also examined.     

N-oleoyl heparin inhibits the amidolytic activity of plasmin and urokinase.

N-desulphated heparin, partially N-acylated on average with three oleoyl chains per molecule, inhibits the amidolytic activity of plasmin (IC50 16 nM) and urokinase (IC50 10mM) when assayed on N-p-tosyl-Gly-Pro-Lys-4-nitroanilide and benzoyl-Ala-Gly-Arg-4-nitroanilide substrates respectively. N-desulphated heparin is not inhibitory. This effect requires the covalent binding of oleoyl residues to heparin and it decreases with increasing concentration of Tris-HCl and non-ionic detergents.     

Effect of Ceramide on Nonraft Proteins

The currently accepted model of biological membranes involves a heterogeneous, highly dynamic organization, where certain lipids and proteins associate to form cooperative platforms (“rafts”) for cellular signaling or transport processes. Ceramides, a lipid species occurring under conditions of cellular stress and apoptosis, are considered to stabilize these platforms, thus modulating cellular function. The present study focuses on a previously unrecognized effect of ceramide generation. In agreement with previous studies, we find that ceramide leads to a depletion of sphingomyelin from mixtures with palmitoyl oleoyl phosphatidylcholine bilayers, forming a ceramide–sphingomyelin-rich gel phase that coexists with a fluid phase rich in palmitoyl oleoyl phosphatidylcholine. Interestingly, however, this latter phase has an almost fourfold smaller bending rigidity compared to a sphingomyelin–palmitoyl oleoyl phosphatidylcholine mixture lacking ceramide. The significant change of membrane bulk properties can have severe consequences for conformational equilibria of membrane proteins. We discuss these effects in terms of the lateral pressure profile concept for a simple geometric model of an ion channel and find a significant inhibition of its activity.     

Daily Oral Oleoyl‐Estrone Gavage Induces a Dose‐Dependent Loss of Fat in Wistar Rats

Objective: To establish whether single daily oral doses of oleoyl‐estrone result in dose‐dependent slimming effects on normal weight rats, and to determine the changes in energy parameters induced by this treatment. Research Methods and Procedures: The effects of a daily oral gavage of oleoyl‐estrone (0, 0.2, 0.5, 1, 2, 5, 10, and 20 μmol/kg per day) in 0.2 ml of sunflower oil given over a 10‐day period were studied in groups, each of which contained six adult female Wistar rats initially weighing 190 to 230 g. A group of intact control rats receiving no gavage was included for comparison. Body weight and food intake were measured daily. Rats were killed on day 10 of treatment, and body composition (protein nitrogen, lipids, and water), liver lipids, and plasma parameters (glucose, triacylglycerols, total cholesterol, free fatty acids, 3‐hydroxybutyrate, urea, aspartate, alanine transaminases, insulin, leptin, and free and acyl‐estrone) were measured. Results: The administration of oleoyl‐estrone resulted in a dose‐dependent loss of body fat, because of a partly maintained energy expenditure combined with decreased food intake. The differences in the energy budget were met by internal fat pools. The changes recorded did not affect the levels of the main plasma energy homeostasis indicators: unaltered glucose, triacylglycerols, free fatty acids, 3hydroxybutyrate, and urea. Protein was accrued even under conditions of severe lipid store drainage. There were no changes in transaminases. No lipid accumulation was recorded in the liver. Plasma insulin and leptin levels decreased with increased oleoyl‐estrone doses, whereas the levels of free and esterified estrone increased with treatment, although not in proportion to the dose received. Discussion: Oral treatment with oleoyl‐estrone resulted in the specific dose‐related loss of fat reserves with little change to other metabolic parameters. These results agree with the postulated role of oleoyl‐estrone as a ponderostat signal.     

Lysophosphatidate Acyltransferase in the Microsomes from Maturing Seeds of Meadowfoam (Limnanthes alba)

Lysophosphatidate (LPA) acyltransferase (EC 2.3. 1.51) in the microsomes from the maturing seeds of meadowfoam (Limnanthes alba), nasturtium (Tropaeolum majus), palm (Syagrus cocoides), castor bean (Ricinus communis), soybean (Glycine max), maize (Zea mays), and rapeseed (Brassica napus) were tested for their specificities toward 1-oleoyl-LPA or 1-erucoyl-LPA, and oleoyl coenzyme A (CoA) or erucoyl CoA. All the enzymes could use either of the two acyl acceptors and oleoyl CoA, but only the meadowfoam enzyme could use erucoyl CoA as the acyl donor to produce dierucoyl phosphatidic acid (PA). The meadowfoam enzyme was studied further. It had an optimal activity at pH 7 to 8, and its activity was inhibited by 1 millimolar MnCl₂, ZnCl₂, or p-chloromercuribenzoate. In a test of substrate specificity using increasing concentrations of either 1-oleoyl-LPA or 1-erucoyl-LPA, and either oleoyl CoA or erucoyl CoA, the enzyme activity in producing PA was highest for dioleoyl-PA, followed successively by 1-oleoyl-2-erucoyl-PA, dierucoyl-PA, and 1-erucoyl-2-oleoyl-PA. In a test of substrate selectivity using a fixed combined concentration, but varying proportions, of 1-oleoyl-LPA and 1-erucoyl-LPA, and of oleoyl CoA and erucoyl CoA, the enzyme showed a pattern of acyl preference similar to that observed in the test of substrate specificity, but the preference toward oleoyl moiety in the substrates was slightly stronger. The meadowfoam microsomes could convert [¹⁴C]glycerol-3-phosphate to diacylglycerols and triacylglycerols in the presence of erucoyl CoA. The meadowfoam LPA acyltransferase is unique in its ability to produce dierucoyl-PA, and should be a prime candidate for use in the production of trierucin oils in rapeseed via genetic engineering.