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Phospholipid biosynthesis in human platelets. Formation of phosphatidylcholine from 1-acyl lysophosphatidylcholine by acyl-CoA:1-acyl-sn-glycero-3-phosphocholine acyltransferase.

Arachidonic acid and other fatty acids are taken up by human platelets from plasma and incorporated into membrane phospholipids. However, little is known about the mechanism and specificity of the various steps of fatty acid insertion into phospholipid. Previous findings from this laboratory have shown that the incorporation of radioactive C20-unsaturated fatty acids (arachidonic, 8,11,14-eicosatrienoic, and 5,8,11,14,17-eicosapentaenoic) into the phospholipids of "resting"p platelets is more rapid than that of the radioactive C16- and C18-saturated and unsaturated fatty acids. We now provide evidence that human platelet microsomes contain acyl-CoA:1-acyl-sn-glycero-3-phosphocholine acyltransferase. The enzyme preparation has a pH optimum of 7.0. Activity is insensitive to 1 mM EDTA and is inhibited 37% by 1 mM Ca2+ and 20% by 1 mM Mg2+. Maximal activity is observed at 100 microM 1-acyl lysophosphatidylcholine at several concentrations of fatty acyl-CoA esters. Apparent Km values from 1.05 to 5.70 microM were obtained for saturated and unsaturated fatty acyl group donors in the presence of 100 microM 1-acyl lysophosphatidylcholine as fatty acyl group acceptor. Comparison of the apparent Vmax values showed that unsaturated CoA esters were transferred more rapidly to 1-acyl lysophosphatidylcholine than saturated CoA esters. Oleate, linoleate, and arachidonate, the major unsaturated fatty acids in platelet phosphatidylcholine, were transferred at similar rates. 8,11,14-eicosatrienoate was transferred about two times faster than these three fatty acyl groups. The data indicate that the incorporation of unsaturated fatty acids into phosphatidylcholine by human platelets occurs via reacylation of 1-acyl lysophosphatidylcholine.

1-Acylglycerophosphocholine O-Acyltransferase↗

Stearoyl-acyl carrier protein and unusual acyl-acyl carrier protein desaturase activities are differentially influenced by ferredoxin.

Acyl-acyl carrier protein (ACP) desaturases function to position a single double bond into an acyl-ACP substrate and are best represented by the ubiquitous Delta9 18:0-ACP desaturase. Several variant acyl-ACP desaturases have also been identified from species that produce unusual monoenoic fatty acids. All known acyl-ACP desaturase enzymes use ferredoxin as the electron-donating cofactor, and in almost all previous studies the photosynthetic form of ferredoxin rather than the non-photosynthetic form has been used to assess activity. We have examined the influence of different forms of ferredoxin on acyl-ACP desaturases. Using combinations of in vitro acyl-ACP desaturase assays and [(14)C]malonyl-coenzyme A labeling studies, we have determined that heterotrophic ferredoxin isoforms support up to 20-fold higher unusual acyl-ACP desaturase activity in coriander (Coriandrum sativum), Thunbergia alata, and garden geranium (Pelargonium x hortorum) when compared with photosynthetic ferredoxin isoforms. Heterotrophic ferredoxin also increases activity of the ubiquitous Delta9 18:0-ACP desaturase 1.5- to 3.0-fold in both seed and leaf extracts. These results suggest that ferredoxin isoforms may specifically interact with acyl-ACP desaturases to achieve optimal enzyme activity and that heterotrophic isoforms of ferredoxin may be the in vivo electron donor for this reaction.

Acyl Carrier Protein↗

Activation of long chain fatty acids with acyl carrier protein: demonstration of a new enzyme, acyl-acyl carrier protein synthetase, in Escherichia coli.

A soluble enzyme activity which catalyzes the synthesis of acyl-acyl carrier protein from acyl carrier proteins, a long chain fatty acid, and ATP has been demonstrated in E. coli. The reaction requires high concentrations of both Ca++ and Mg++ for activity, and cleaves ATP to AMP and PPi. The fatty acyl product has been identified as acyl-acyl carrier protein by its solubility, thioester linkage, molecular weight, charge, and biological activity. Several criteria indicate the enzyme is distinct from acyl-CoA synthetase. The fatty acid specificity of the enzyme suggests a role of acyl-acyl carrier protein synthetase in the incorporation of fatty acids into phospholipid.

Adenosine Triphosphate↗

Preparation of fatty-acylated derivatives of acyl carrier protein using Vibrio harveyi acyl-ACP synthetase.

A simple two-step purification of Vibrio harveyi fatty acyl-acyl carrier protein (acyl-ACP) synthetase, which is useful for the quantitative preparation and analysis of fatty-acylated derivatives of ACP, is described. Acyl-ACP synthetase can be partially purified from extracts of this bioluminescent bacterium by Cibacron blue chromatography and Sephacryl S-300 gel filtration and is stable for months at -20 degrees C in the presence of glycerol. Incubation of ACP from Escherichia coli with ATP and radiolabeled fatty acids (6 to 16 carbons in length) in the presence of the enzyme resulted in quantitative conversion to biologically active acylated derivatives. The enzyme reaction can be monitored by a filter disk assay to quantitate levels of ACP or by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography to detect ACP in cell extracts. With its broad fatty acid chain length specificity and optimal activity in mild nondenaturing buffers, the soluble V. harveyi acyl-ACP synthetase provides an attractive alternative to current chemical and enzymatic methods of acyl-ACP preparation and analysis.

Acyl Carrier Protein↗

A comparison of the acylation of 1-acyl-sn-glycero-3-phosphoinositol and 1-acyl-sn-glycero-3-phosphocholine in neuronal nuclei in vitro using radioactive arachidonate and oleate.

A neuronal nuclear fraction (N1) was isolated from cerebral cortices of 15-day-old rabbits. Samples of N1 were incubated with a radioactive fatty acid ([3H]arachidonate or [14C]oleate), acylation cofactors, and 1-acyl-sn-glycero-3-phosphoinositol (1-acyl-GPI) or 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC). In competition studies, both radioactive fatty acids were incubated with one lysophospholipid or the two lysophospholipids were incubated with one radioactive fatty acid. Using [3H] arachidonate and one lysophosphoglyceride, a maximal rate of incorporation into phosphatidylinositol (PI) was found at a relatively low concentration of 1-acyl-GPI (10 microM), while increasing rates of incorporation into phosphatidylcholine (PC) were seen with increasing concentrations of 1-acyl-GPC (to 65 microM). At low concentrations of lysophosphoglyceride (less than or equal to 25 microM) the rate of arachidonate incorporation into PI greatly exceeded rates of arachidonate incorporation into PC. This higher rate of arachidonate incorporation into PI was also seen in incubations where both lysophospholipids were present. For oleate, greater rates of incorporation into PC were found in comparison with rates of labelling of PI in assays using relatively high concentrations of one or both lysophospholipids. When comparing arachidonate and oleate, in assays with one or both fatty acids, the polyunsaturate showed at least threefold higher rates of incorporation into PI. For PC labelling higher rates of arachidonate incorporation were evident at the higher concentrations of 1-acyl-GPC and the superiority over oleate was not as marked as that seen in PI labelling.

Acylation↗

Regulation of malonyl-CoA metabolism by acyl-acyl carrier protein and beta-ketoacyl-acyl carrier protein synthases in Escherichia coli.

The cessation of phospholipid biosynthesis by the inhibition of the sn-glycerol-3-phosphate acyltransferase using a plsB mutant led to an accumulation of long chain acyl-acyl carrier proteins (acyl-ACP) and the concomitant inhibition of de novo fatty acid biosynthesis in Escherichia coli. Malonyl-CoA did not accumulate when phospholipid and fatty acid synthesis was blocked. However, the inactivation of beta-ketoacyl-ACP synthases I and II with the antibiotic cerulenin triggered a large increase in the accumulation of malonyl-CoA following the cessation of phospholipid synthesis, illustrating that the beta-ketoacyl-ACP synthases were responsible for the degradation of malonyl-CoA in the presence of long chain acyl-ACP. The acyl-ACP requirement for malonyl-CoA degradation activity was confirmed by shifting enoyl-ACP reductase mutants (fabI(Ts)) to the non-permissive temperature, leading to the abrupt cessation of fatty acid synthesis and the accumulation of malonyl-CoA in the absence of cerulenin. Analysis of the ACP pool composition before and after the temperature shift showed that the fabI block did not result in the accumulation of long chain acyl-ACP. These data indicate a feedback regulatory loop that functions to recycle malonyl-CoA to acetyl-CoA following the down-regulation of fatty acid and phospholipid formation and provides a physiological rationale for the acyl-ACP-dependent, malonyl-ACP decarboxylase reaction catalyzed by beta-ketoacyl-ACP synthases I and II.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

Acylation of lysophosphatidylcholine in bovine heart muscle microsomes: purification and kinetic properties of acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase.

Bovine heart muscle microsomes rapidly convert lysophosphatidylcholine (LPC) into phosphatidylcholine (PC) in the presence of oleoyl-CoA. Both substrates are incorporated into the product, although the rate of incorporation of radiolabel into PC from 1-[14C]palmitoyl-LPC was approximately threefold higher than the rate of incorporation from [14C]oleoyl-CoA. Furthermore, the rate of incorporation of radiolabel from [14C]LPC was stimulated fivefold by the presence of oleoyl-CoA. These results demonstrate the presence of both acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase (EC 2.3.1.23) and an LPC:LPC transacylase (EC 3.1.1.5) in microsomes. Separation of the two enzymatic activities and purification of the acyltransferase was achieved by a procedure involving extraction with 3-[3-cholamidopropyl)dimethylammonio)-1-propanesulfonate detergent and chromatography on DEAE-cellulose, Reactive blue agarose, and Matrex gel green A. The isolated acyltransferase was a single species of 64,000 Da as judged by polyacrylamide gel electrophoresis in the presence of dodecyl sulfate. The substrate specificity of the enzyme was studied by using a series of lysophospholipids as acyl acceptors and acyl-CoA derivatives as acyl donors. The enzyme was catalytically active with LPC as acyl acceptor but displayed little or no activity with lysophosphatidylethanolamine, lysophosphatidylinositol, or lysophosphatidylserine. Of the LPC derivatives tested, the highest activity was obtained with 1-palmitoyl-LPC. Wider specificity was exhibited for the nature of the acyl donor, for which arachidonoyl-CoA, linoleoyl-CoA, and oleoyl-CoA were highly active substrates. These properties of the acyltransferase are in accord with a role of the enzyme in determining the composition of PC in myocardium.

1-Acylglycerophosphocholine O-Acyltransferase↗

Synthesis of 1-palmitoyl and 1-stearoyl phosphatidylcholines from mixtures of acyl acceptors via acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in liver microsomes.

The fatty acid selectivity of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase in rat liver microsomes was studied using a mixture of the [1-(3)H]palmitoyl plus [1-(14C)stearoyl molecular species of 1-acylglyceryl-phosphorylcholine. At a 1-acyl-sn-glycero-3-phosphorylcholine concentration of 0.16 mM, the enzyme exhibited a selectivity of 3.5-fold for the 1-palmitoyl over the 1-stearoyl species of the acyl acceptor and reaction velocities with linoleoyl- and arachidonoyl-CoA were 38--47% greater than with oleoyl-CoA. Lowering the acceptor concentration to 0.016 mM gave reaction rates with the polyenoic thiolesters which were 174--187% greater than with oleoyl-CoA and the 1-palmitoyl-sn-glycero-3-phosphorylcholine was preferred by 2.2, 1.6, and 1.6-fold with oleoyl-, linoleoyl- and arachidonoyl-CoA, respectively. The results support the potential importance of the fatty acid selectivities of the acyl-CoA:1-acyl-sn-glycero-3-phosphorylcholine acyltransferase towards both acyl acceptor and donor in regulating the phosphatidylcholine species formed by the reaction in vivo.

1-Acylglycerophosphocholine O-Acyltransferase↗

Promiscuous fatty acyl CoA ligases produce acyl-CoA and acyl-SNAC precursors for polyketide biosynthesis.

The study of bioactive natural products has undergone rapid advancement with the cloning and sequencing of large number of gene clusters and the concurrent progress to manipulate complex biosynthetic systems in heterologous hosts. The genetic reconstitution necessitates that the heterologous hosts possess substrate pools that could be coordinately supplied for biosynthesis. Polyketide synthases (PKS) utilize acyl-coenzyme A (CoA) precursors and synthesize polyketides by repetitive decarboxylative condensations. Here we show that acyl-CoA ligases, which belong to a large family of acyl-activating enzymes, possess potential to produce varied starter CoA precursors that could be utilized in polyketide biosynthesis. Incidentally, such protein domains have been recognized in several PKS and nonribosomal peptide synthetase gene clusters. Our studies with mycobacterial fatty acyl-CoA ligases (FACLs) show remarkable tolerance to activate a variety of fatty acids that contain modifications at alpha, beta, omega, and omega-nu positions. This substrate flexibility extends further such that these proteins also efficiently utilize N-acetyl cysteamine, the shorter acceptor terminal portion of CoASH, to produce acyl-SNACs. We show that the in situ generated acyl-CoAs and acyl-SNACs could be channeled to types I and -III PKS systems to produce new metabolites. Together, the promiscuous activity of FACL and PKSs provides new opportunities to expand the repertoire of natural products.

Acetyl Coenzyme A↗

Substrate activating mechanism of short-chain acyl-CoA, medium-chain acyl-CoA, long-chain acyl-CoA, and isovaleryl-CoA dehydrogenases from bovine liver: a resonance Raman study on the 3-ketoacyl-CoA complexes.

We have shown previously that acetoacetyl-CoA bound to medium-chain acyl-CoA dehydrogenase from pig kidney is transformed into an enolate form, O = C(3)-C(2)H = C(1)-O-, and that the interaction between the C(4a) = N(5) moiety of flavin and the O = C(3)-C(2)H = C(1)-O- moiety of acetoacetyl-CoA is important for the charge-transfer interaction [Nishina, Y. et al. (1992) J. Biochem. 111, 699-706]. In this study, we examined four kinds of acyl-CoA dehydrogenases [short-chain acyl-CoA (SCAD), medium-chain acyl-CoA (MCAD), long-chain acyl-CoA (LCAD), and isovaleryl-CoA (IVD) dehydrogenases] from bovine liver. The Raman spectra of non-labeled and isotopically labeled acetoacetyl-CoA in keto-form revealed that the 1,716-cm-1 and 1,650-cm-1 bands were derived from the C(3) = O and the C(1) = O stretching mode, respectively. In the charge-transfer complexes of acetoacetyl-CoA with the four kinds of dehydrogenases, the resonance Raman (RR) bands corresponding to the C(3) = O and the C(1) = O of acetoacetyl-CoA were observed at around 1,643-1,622 and 1,506-1,476 cm-1, respectively, indicating that acetoacetyl-CoA was transformed into the enolate form as the result of the complexation with the enzymes. Further, in RR spectra with excitation at 632.8 nm, within the charge-transfer band of the complexes of acetoacetyl-CoA with the four acyl-CoA dehydrogenases, both bands associated with the C(4a) = N(5) moiety of oxidized flavin and the O = C(3)-C(2)H = C(1)-O- moiety of acetoacetyl-CoA were enhanced, but the benzene portion of oxidized flavin was not. These results indicate that the substrate activating mechanism is common to all four kinds of dehydrogenases, i.e., the interaction between the C(1) = O of acetoacetyl-CoA and the positively polarized atoms of the enzymes located in close proximity to the oxygen atom of C(1) = O is important, and the C(4a) = N(5) moiety of flavin participates in the interaction. Some kinds of 3-ketoacyl-CoAs were tested instead of acetoacetyl-CoA and essentially similar results were obtained. The positions of the bands derived from the C(1)-O- moiety of 3-ketoacyl-CoAs were different by ca. 30 cm-1 in two groups, i.e., ca. 1,475 cm-1 for SCAD and MCAD and ca. 1,505 cm-1 for LCAD and IVD, that is, RR spectra can classify the four dehydrogenases into two groups.

Acyl-CoA Dehydrogenase↗

Presence of three acyl-CoA oxidases in rat liver peroxisomes. An inducible fatty acyl-CoA oxidase, a noninducible fatty acyl-CoA oxidase, and a noninducible trihydroxycoprostanoyl-CoA oxidase.

Mammalian liver peroxisomes are capable of beta-oxidizing a variety of substrates including very long chain fatty acids and the side chains of the bile acid intermediates di- and trihydroxycoprostanic acid. The first enzyme of peroxisomal beta-oxidation is acyl-CoA oxidase. It remains unknown whether peroxisomes possess one or several acyl-CoA oxidases. Peroxisomal oxidases from rat liver were partially purified by (NH4)2SO4 precipitation and heat treatment, and the preparation was subjected to chromatofocusing, chromatography on hydroxylapatite and dye affinity matrices, and gel filtration. The column eluates were assayed for palmitoyl-CoA and trihydroxycoprostanoyl-CoA oxidase activities and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The results revealed the presence of three acyl-CoA oxidases: 1) a fatty acyl-CoA oxidase with a pI of 8.3 and an apparent molecular mass of 145 kDa. The enzyme consisted mainly of 52- and 22.5-kDa subunits and could be induced by clofibrate treatment; 2) a noninducible fatty acyl-CoA oxidase with a pI of 7.1 and an apparent molecular mass of 427 kDa. It consisted mainly, if not exclusively, of one polypeptide component of 71 kDa; and 3) a noninducile trihydroxycoprostanoyl-CoA oxidase with a pI of 7.1 and an apparent molecular mass of 139 kDa. It consisted mainly, if not exclusively, of one polypeptide component of 69 kDa. Our findings are probably related to the recent discovery of two species of acyl-CoA oxidase mRNA in rat liver (Miyazawa, S., Hayashi, H., Hijikata, M., Ishii, N., Furata, S., Kagamiyama, H., Osumi, T., and Hashimoto, T. (1987) J. Biol. Chem. 262, 8131-8137) and they probably also explain why in human peroxisomal beta-oxidation defects an accumulation of very long chain fatty acids is not always accompanied by an excretion of bile acid intermediates and vice versa.

Acyl-CoA Oxidase↗

Acyl carrier protein from Escherichia coli. Structural characterization of short-chain acylated acyl carrier proteins by NMR.

Acylated acyl carrier proteins (ACPs) with acyl chain lengths of 2, 4, 6, 8, and 10 carbons were investigated by NMR and nuclear Overhauser methods at 500 MHz. Chemical shift changes of downfield aromatic and upfield, ring-current-shifted, isoleucine proton resonances monotonically vary as a function of acyl chain length with the most prominent shifts occurring with chain lengths between four and six carbons. Chemical shifts are largest for one of the two phenylalanines; however, substantial shifts do exist for Tyr-71, His-75, and two isoleucines. Since these residues are distributed throughout the molecule, their associated resonance chemical shifts are most probably explained by an induced conformational change. Comparative NOE measurements on reduced ACP (ACP-SH) and ACP-S-C8 suggest, however, that these induced conformational changes are small except for around one of the phenylalanines. A tertiary structural model for acyl-ACP consistent with our previous model for ACP-SH [Mayo, K. H., Tyrell, P. M., & Prestegard, J. H. (1983) Biochemistry 22, 4485-4493] is presented.

Acyl Carrier Protein↗

Phospholipid dependence of rat liver microsomal acyl:CoA synthetase and acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase.

Investigations were performed on the influence of the phospholipid composition and physicochemical properties of the rat liver microsomal membranes on acyl-CoA synthetase and acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase activities. The phospholipid composition of the membranes was modified by incubation with different phospholipids in the presence of lipid transfer proteins or by partial delipidation with exogenous phospholipase C and subsequent enrichment with phospholipids. The results indicated that the incorporation of phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine induced a marked activation of acyl-CoA synthetase for both substrates used--palmitic and oleic acids. Sphingomyelin occurred as specific inhibitor for this activity especially for palmitic acid. Palmitoyl-CoA: and oleoyl-CoA: 1-acyl-sn-glycero-3-phosphocholine acyltransferase activities were found to depend on the physical state of the membrane lipids. The alterations in the membrane physical state were estimated using two different fluorescent probes--1,6-diphenyl-1,3,5-hexatriene and pyrene. In all cases of membrane fluidization this activity was elevated. On the contrary, in more rigid membranes obtained by incorporation of sphingomyelin and dipalmitoylphosphatidylcholine, acyltransferase activity was reduced for both palmitoyl-CoA and oleoyl-CoA. We suggest a certain similarity in the way of regulation of membrane-bound acyltransferase and phospholipase A2 which both participate in the deacylation-reacylation cycle.

1-Acylglycerophosphocholine O-Acyltransferase↗

Photoaffinity Labeling of Developing Jojoba Seed Microsomal Membranes with a Photoreactive Analog of Acyl-Coenzyme A (Acyl-CoA) (Identification of a Putative Acyl-CoA:Fatty Alcohol Acyltransferase.

Jojoba (Simmondsia chinensis, Link) is the only plant known that synthesizes liquid wax. The final step in liquid wax biosynthesis is catalyzed by an integral membrane enzyme, fatty acyl-coenzyme A (CoA):fatty alcohol acyltransferase, which transfers an acyl chain from acyl-CoA to a fatty alcohol to form the wax ester. To purify the acyltransferase, we have labeled the enzyme with a radioiodinated, photoreactive analog of acyl-CoA, 12-[N-(4-azidosalicyl)amino] dodecanoyl-CoA (ASD-CoA). This molecule acts as an inhibitor of acyltransferase activity in the dark and as an irreversible inhibitor upon exposure to ultraviolet light. Oleoyl-CoA protects enzymatic activity in a concentration-dependent manner. Photolysis of microsomal membranes with labeled ASD-CoA resulted in strong labeling of two polypeptides of 57 and 52 kD. Increasing concentrations of oleoyl-CoA reduced the labeling of the 57-kD polypeptide dramatically, whereas the labeling of the 52-kD polypeptide was much less responsive to oleoyl-CoA. Also, unlike the other polypeptide, the labeling of the 57-kD polypeptide was enhanced considerably when photolyzed in the presence of dodecanol. These results suggest that a 57-kD polypeptide from jojoba microsomes may be the acyl-CoA:fatty alcohol acyltransferase.

Journal Article↗

Yeast acyl-CoA-binding protein: acyl-CoA-binding affinity and effect on intracellular acyl-CoA pool size.

Acyl-CoA-binding protein (ACBP) is a 10 kDa protein characterized in vertebrates. We have isolated two ACBP homologues from the yeast Saccharomyces carlsbergensis, named yeast ACBP types 1 and 2. Both proteins contain 86 amino acid residues and are identical except for four conservative substitutions. In comparison with human ACBP, yeast ACBPs exhibit 48% (type 1) and 49% (type 2) conservation of amino acid residues. The amino acid sequence of S. carlsbergensis ACBP type 1 was found to be identical with the one ACBP present in Saccharomyces cerevisiae. A recombinant form of this protein was expressed in Escherichia coli and S. cerevisiae, purified, and its acyl-CoA-binding properties were characterized by isoelectric focusing and microcalorimetric analyses. The yeast ACBP was found to bind acyl-CoA esters with high affinity (Kd 0.55 x 10(-10) M). Overexpression of yeast ACBP in S. cerevisiae resulted in a significant expansion of the intracellular acyl-CoA pool. Finally, Southern-blotting analysis of the two genes encoding ACBP types 1 and 2 in S. carlsbergensis strongly indicated that this species is a hybrid between S. cerevisiae and Saccharomyces monacensis.

Acyl Coenzyme A↗

Role of acyl-CoA binding protein in acyl-CoA metabolism and acyl-CoA-mediated cell signaling.

Long-chain acyl-CoA esters (LCA) act both as substrates and intermediates in metabolism and as regulators of various intracellular functions. Acyl-CoA binding protein (ACBP) binds LCA with high affinity and is believed to play an important role in intracellular acyl-CoA transport and pool formation and therefore also for the function of LCA as metabolites and regulators of cellular functions . The free concentration of cytosolic LCA is efficiently buffered to low nanomole concentration by ACBP and fatty acid binding protein (FABP). An additional important factor is the activity of acyl-CoA hydrolases. The estimated cellular free LCA concentration is two to four orders of magnitude lower than the concentrations reported to be necessary to regulate most LCA-affected cellular functions. Preliminary evidence indicates that the regulatory effect of LCA might be mediated by the LCA/ACBP complex.

Acyl Coenzyme A↗