The binding of L-tryptophan to serum albumins in the presence of non-esterified fatty acids.

Bovine, human and rat serum albumins were defatted and palmitic acid, oleic acid and lauric acid added in various molar ratios. The binding of L-tryptophan to these albumins was measured at 20 degrees C in a 0.138 M salt solution at pH 7.4, by using an ultrafiltration technique, and analysed in terms of n, the number of available tryptophan-binding sites per albumin molecule, with apparent association constant, k. 2. n and k were 0.90 and 2.3x10(-4)M(minus-1) respectively for defatted bovine serum albumin and 0.87 and 9.7x10(-3)M(-minus-1) for human albumin. Addition of palmitic acid did not decrease n until the molar ratio, fatty acid/bovine albumin, approached and exceeded 2. The decrease in k was small and progressive. In contrast, lauric caused a marked decrease in n and k at ratios as low as 0.5. A similar distinction between the effects on n of palmitic acid and oleic acid and those of lauric acid was seen for human albumin. k for human albumin was not significantly affected by fatty acids under the conditions studied. 3. It is concluded that primary long-chain fatty acid sites interact only weakly with the tryptophan site on albumin and that inhibition of tryptophan binding occurs when secondary long-chain sites are occupied. Primary medium-chain fatty acid sites are distinct from primary long-chain sites but may be grouped with secondary long-chain sites. 4. The relationship between free and bound tryptophan in samples of rat plasma (Stoner et al., 1975) is discussed in terms of a similar but limited study of rat albumin.     

Steroid-protein interactions. 40. The effect of fatty acids on progesterone binding to human serum albumin

Human serum albumin was delipidated by solvent extraction or by treatment with charcoal. Progesterone complexes formed with these albumin preparations had higher association constants than those formed with the untreated samples. The charcoal method of delipidation resulted in somewhat higher affinity constants than extraction with chloroform/methanol. Addition of 5 mol lauric acid per mol albumin reduced the association constant of the progesterone complex by approx. 50%. Studies with lauric, myristic, and palmitic acid showed that the decrease of binding affinity for progesterone was proportional to the amount of fatty acid added to albumin, and to its chain length. These results confirm and extend our previous findings of inhibition of progesterone binding to human albumin by long-chain fatty acids.     

Uptake of fatty acids by the yeasts, Saccharomyces uvarum and Saccharomycopsis lipolytica

Yeast cells take up exogenous fatty acids with subsequent rapid incorporation into glycerolipids. beta-Oxidation does not occur in Saccharomyces uvarum and is observed in Saccharomycopsis lipolytica only 2-5 min after addition of radioactively labeled fatty acid. Rates of fatty acid uptake are linear up to 30 s with S. lipolytica and up to 2 min with S. uvarum. The uptake kinetics are consistent with a dual mode of transport, comprising a saturable component with KT values in the range 10(-5)-10(-6) M, and apparently simple diffusion that predominates at high substrate concentrations. Kinetics of fatty acid permeation are independent of metabolic energy and membrane potential. At least two fatty acid carrier systems exist in both S. lipolytica and S. uvarum, one being specific for fatty acids with 12 and 14 C atoms, respectively, the other for C16 and C18 saturated or unsaturated fatty acids. Octanoic acid and decanoic acid are not taken up by S. lipolytica. Internalization of lauric acid and oleic acid by S. lipolytica cells is preceded by a rapid (less than 5 s) initial uptake which most likely represents irreversible adsorption. This phenomenon was not observed with heat-inactivated S. lipolytica cells or with viable S. uvarum. In azide-poisoned cells of S. lipolytica an up to 20-fold accumulation of unesterified fatty acid was observed within 30 s after the addition of substrate.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

Interaction of rat alpha-fetoprotein and albumin with polyunsaturated and other fatty acids: determination of apparent association constants

The interaction of fatty acids with rat alpha-fetoprotein and albumin was measured using a partition equilibrium method. alpha-Fetoprotein (AFP) displays one high-affinity binding site for fatty acids and albumin near two binding sites. The AFP association constants for most fatty acids were similar to those of albumin (in the 10(7) M-1 range) whereas for docosahexaenoic acid it was 9.7 x 10(8) M-1, about 50-fold higher than that corresponding to albumin. This difference justifies docosahexaenoic acid in fetal or neonatal serum being mainly bound to AFP and can indicate a highly specific role of AFP in the transport of this fatty acid.     

Fatty acids binding to albumin increases its uptake and transcytosis by the lung capillary endothelium

To determine whether uptake and transcytosis of albumin (A) in continuous capillary endothelia are modified when this protein carries fatty acids, the transport of albumin-oleic acid and albumin-palmitic acid complexes was compared with that of defatted albumin. The probes, either radioiodinated or tagged with 5-nm gold particles (Au), or both, were perfused in situ or injected in vivo; after 3 or 30 min lung fragments were radioassayed or examined by electron microscopy. Both in situ and in vivo, the uptake of fatty acid-carrying albumin (A-FA) was consistently 2 to 3 times higher than that of defatted A. Electron microscopy revealed that A-FA complexes tagged with gold were taken up and transported across the endothelium by plasmalemmal vesicles. Morphometric analysis showed that as compared with A-Au, at 3 min the density of (A-FA)Au bound to plasmalemmal vesicles was 2 to 3 times higher, and the extent of transcytosis was increased. Uptake of the iodinated albumin was more effectively competed by A-FA complexes than by defatted A, suggesting a higher affinity of the former for the albumin binding sites of the endothelium. The results indicate that when carrying fatty acids, albumin is taken up specifically and with high affinity by the capillary endothelium, a process that may play a role in the transport of fatty acids from the plasma to the cells where they are metabolized.     

Candida cloacae oxidation of long-chain fatty acids to dioic acids

Candida cloacae cells oxidize long-chain fatty acids to their corresponding dicarboxylic acids (dioic acids) at rates dependent on their chain length and degree of saturation. This is despite the well-known toxicity of the fatty acids. Among the saturated substrates, the oxidation is limited to lauric acid (C12). The addition of pristane (5% v/v), which acts as an inert carrier for the poorly water-soluble substrate, boosts the oxidation of lauric acid to a rate that is comparable to that of dodecane. When dissolved in pristane, myristic (C14) and palmitic (C16) acids are effective carbon sources for C. cloacae, but dioic acid production is very low. Media glucose concentration and pH also influence cell growth and productivity. After the glucose is depleted, oxidation is optimal at a low pH. A two-phase (pristane/water) reaction was tested in a 2-l stirred tank bioreactor in which growth and oxidation were separated. A 50% w/w conversion of lauric acid (10 g/l) to dodecanedioic acid was achieved. The bioreactor also alleviated poor mass transfer characteristics experienced in shake flasks.     

Peroxisomes contribute to the acylcarnitine production when the carnitine shuttle is deficient

Fatty acid β-oxidation may occur in both mitochondria and peroxisomes. While peroxisomes oxidize specific carboxylic acids such as very long-chain fatty acids, branched-chain fatty acids, bile acids, and fatty dicarboxylic acids, mitochondria oxidize long-, medium-, and short-chain fatty acids. Oxidation of long-chain substrates requires the carnitine shuttle for mitochondrial access but medium-chain fatty acid oxidation is generally considered carnitine-independent. Using control and carnitine palmitoyltransferase 2 (CPT2)- and carnitine/acylcarnitine translocase (CACT)-deficient human fibroblasts, we investigated the oxidation of lauric acid (C12:0). Measurement of the acylcarnitine profile in the extracellular medium revealed significantly elevated levels of extracellular C10- and C12-carnitine in CPT2- and CACT-deficient fibroblasts. The accumulation of C12-carnitine indicates that lauric acid also uses the carnitine shuttle to access mitochondria. Moreover, the accumulation of extracellular C10-carnitine in CPT2- and CACT-deficient cells suggests an extramitochondrial pathway for the oxidation of lauric acid. Indeed, in the absence of peroxisomes C10-carnitine is not produced, proving that this intermediate is a product of peroxisomal β-oxidation. In conclusion, when the carnitine shuttle is impaired lauric acid is partly oxidized in peroxisomes. This peroxisomal oxidation could be a compensatory mechanism to metabolize straight medium- and long-chain fatty acids, especially in cases of mitochondrial fatty acid β-oxidation deficiency or overload.     

Expression of lauroyl-acyl carrier protein thioesterase in brassica napus seeds induces pathways for both fatty acid oxidation and biosynthesis and implies a set point for triacylglycerol accumulation

Expression of a California bay lauroyl-acyl carrier protein thioesterase (MCTE) in developing seeds of transgenic oilseed rape alters the fatty acid composition of the mature seed, resulting in up to 60 mol% of laurate in triacylglycerols. In this study, we examined the metabolism of lauric acid and 14C-acetate in developing seeds of oilseed rape that express high levels of MCTE. Lauroyl-CoA oxidase activity but not palmitoyl-CoA oxidase activity was increased several-fold in developing seeds expressing MCTE. In addition, isocitrate lyase and malate synthase activities were six- and 30-fold higher, respectively, in high-laurate developing seeds. Control seeds incorporated 14C-acetate almost entirely into fatty acids, whereas in seeds expressing MCTE, only 50% of the label was recovered in lipids and the remainder was in a range of water-soluble components, including sucrose and malate. Together, these results indicate that the pathways for beta-oxidation and the glyoxylate cycle have been induced in seeds expressing high levels of MCTE. Although a substantial portion of the fatty acid produced in these seeds is recycled to acetyl-CoA and sucrose through the beta-oxidation and glyoxylate cycle pathways, total seed oil is not reduced. How is oil content maintained if lauric acid is inefficiently converted to triacylglycerol? The levels of acyl carrier protein and several enzymes of fatty acid synthesis were increased two- to threefold at midstage development in high-laurate seeds. These results indicate that a coordinate induction of the fatty acid synthesis pathway occurs, presumably to compensate for the lauric acid lost through beta-oxidation or for a shortage of long-chain fatty acids.     

Thermal stability of fatty acid-serum albumin complexes studied by differential scanning calorimetry.

Differential scanning calorimetry has been used to study the thermal stability of bovine serum albumin as affected by binding of fatty acids (lauric acid and stearic acid) and sodium dodecyl sulfate (SDS). All the ligands stabilized the protein molecules in a similar manner, but to different levels. A maximum increase in denaturation temperature of 30 degrees C was obtained with lauric acid. The thermograms indicate the presence of several ligand-albumin complexes having different heat stabilities. Variations in pH in 0.9% NaCl affected the heat stability of both ligand-poor and ligand-rich albumin, the former being more sensitive to variations in pH within the physiological range. Variations in NaCl concentration affected the thermal stabilities at neutral pH, expecially at low salt concentrations. While ligand-rich albumin was somewhat destabilized by increasing NaCl concentrations, ligand-poor albumin was strongly stabilized. The potential use of differential scanning calorimetry in ligand-albumin research is discussed.     

Bactericidal effect of fatty acids on mycobacteria, with particular reference to the suggested mechanism of intracellular killing

The effect of fatty acids on Mycobacterium smegmatis was examined in vitro at pH 5.0 to 7.0 to determine the role of fatty acids in the intracellular killing of mycobacteria. Unsaturated fatty acids showed strong bactericidal activity in low concentrations (0.005 to 0.02 mM), whereas saturated fatty acids, except for lauric and myristic acids, were not very effective even at a concentration of 0.2 mM. Addition of a saturated fatty acid (palmitic or stearic acid) to an unsaturated fatty acid (oleic or linoleic acid) did not strongly interfere with the bactericidal effect of the unsaturated fatty acid at pH 5.0 and 6.0. Ca2+ (3.0 mM), Mg2+ (1.0 mM), and gamma-globulin (0.4%) showed weak reversal effects on the bactericidal activity of unsaturated fatty acids at pH 5.0 and 6.0. Serum albumin and serum showed strong reversal effects. The concentrations of each fatty acid in a mixture (molar ratio, 1:1:1:1) of oleic, linoleic, palmitic, and stearic acids required for the killing of M. smegmatis in the presence of 2% serum (bovine, rabbit, or human) were 0.05 to 0.10 mM at pH 5.0 and 6.0 and 0.05 to 0.20 mM at pH 7.0, depending on the serum used. The susceptibilities of M. kansasii, M. bovis strain BCG, and M. tuberculosis to the mixture of the four fatty acids in the presence of 2% bovine serum were similar to that of M. smegmatis, although M. fortuitum was more resistant.     

Susceptibility of Clostridium perfringens to C-C fatty acids

AIMS: To determine susceptibility of Clostridium perfringens strains CCM 4435(T) and CNCTC 5459 to C(2)-C(18) fatty acids, and evaluate influence of pH in cultures grown on glucose. Straw particles were added to cultures to simulate the presence of solid phase of the digestive tract milieu. METHODS AND RESULTS: Antimicrobial activity of fatty acids was expressed as a concentration at which only 50% of the initial glucose was utilized. Lauric acid showed the highest antimicrobial activity, followed by myristic, capric, oleic and caprylic acid. Only strain CNCTC 5459 was susceptible to linoleic acid. Neither caproic acid and acids with a shorter carbon chain nor palmitic and stearic acid influenced substrate utilization. The antimicrobial activity of myristic, oleic and linoleic acid decreased when clostridia were grown in the presence of straw particles. In cultures of both strains treated with capric and lauric acid at pH 5.0-5.3, the number of viable cells was <10(2) ml(-1). Only lauric acid reduced number of viable cells of both strains below 10(2) ml(-1) at pH > 6. Transmission electron microscopy revealed separation of inner and outer membranes and cytoplasma disorganization in cells treated with lauric acid. CONCLUSIONS: Lauric acid had the highest activity towards C. perfringens among fatty acid tested. Its activity was not influenced by the presence of solid particles and did not cease at pH > 6. SIGNIFICANCE AND IMPACT OF THE STUDY: Lauric acid might be a means for control of clostridial infections in farm animals.     

Marked acceleration of exogenous fatty acid incorporation into cellular triglycerides by fetuin.

Fetuin belongs to a group of fetal glycoproteins whose specific function is not known. In this study we investigated the effect of bovine fetuin on exogenous fatty acid incorporation into lipid classes by fetal rabbit aortic smooth muscle cells (SMC) and human fetal skin fibroblasts. When compared with albumin, the addition of fetuin to the culture medium caused a dramatic increase in labeled fatty acid incorporation (nanomoles/mg of protein) by SMC into triglycerides (albumin (control) 2.8 +/- 0.3 + fetuin 178.3 +/- 13.7). This effect was noted at a wide range of fetuin concentrations (0.2-5%) at oleate:fetuin molar ratios of 3.3-0.13, respectively. Similar effects were noted using human fetal skin fibroblasts with both labeled oleic and arachidonic acids (0.1 mM) as substrates (arachidonic acid incorporation into triglycerides, albumin (control) 76.9 +/- 16.2 + fetuin 684.6 +/- 64.1). Stimulation of fatty acid incorporation into di- and monoglycerides was also noted. Although the amount of unbound fatty acid in the presence of fetuin was greater than with albumin, experiments done under conditions that create identical unbound oleate levels (by varying fatty acid concentration) still showed increased fatty acid incorporation into triglycerides by SMC when exposed to fetuin. This marked effect of fetuin on triglyceride accumulation in cells was confirmed by lipid analysis, strong positive staining with oil red O, and transmission of electron microscopy. Furthermore, the potential physiological role of fetuin in terms of fatty acid and transport was attested by (a) the presence of significant amounts of free fatty acids associated with fetuin; and (b) by the stimulatory effect of fetuin, even when added to culture media containing other fatty acid carriers. These results show that (a) fetuin is far more efficient than albumin in incorporating fatty acids into cells; and (b) this might represent a novel function for fetuin during development.     

Changes in fatty acid composition during development of tissues of coconut (Cocos nucifera L.) embryos in the intact nut and in vitro.

Intact coconuts were germinated in situ and compared with excised zygotic embryos germinated in vitro. The growth of the embryonic tissue and their fatty acid compositions were measured. Haustoria, plumules and radicles of coconuts germinated in situ grew continuously and proportionately throughout the 120 d experiment with haustauria increasing to 45 g x nut(-1) and weighing 4-5-fold more than the other two tissues. The plumules and radicles of the seedlings cultured in vitro also grew continuously but the haustoria grew sporadically between 15 d and 75 d in culture and, at 250 mg x nut(-1) after 75 d, were smaller than the other two tissues. All the tissues of the nuts grown in situ contained significant amounts of lauric acid, the acid characteristic of coconut oil, as well as longer chain saturated and unsaturated fatty acids. The content of medium and long chain fatty acids increased in all growing tissues as the experiment proceeded, especially the haustorium which contained 24-35% of its fatty acid as lauric acid; the fat content of solid endosperm reduced during this period. Seedlings grown in vitro, on the other hand, failed to accumulate lauric acid in any of their tissues (haustorium contained 6-11% of its fatty acid as lauric acid). The results may have implications for the design of growth media for growing zygotic and somatic cultures of coconut and may provide a marker for successful germination.     

Antibacterial Activity of Long Chain Fatty Acids and the Reversal with Calcium, Magnesium, Ergocalciferol and Cholesterol

SUMMARY: Screening tests indicated that Gram positive bacteria are inhibited by long chain fatty acids. No inhibition was demonstrated with Gram negative bacteria. The minimum inhibitory concentrations (MIC) for a series of the fatty acids are presented. Growth curves in the presence of linolenic acid showed increases in lag phase duration and calcium addition reversed this effect, thus indicating the arbitrary nature of the MIC values. Bactericidal studies showed lauric acid to be the most active saturated fatty acid but the activity was less than that of the C₁₈ unsaturated fatty acids. Oleic acid was more effective than elaidic acid. Calcium ions, cholesterol and ergocalciferol reversed the activities of lauric and linoleic acids but magnesium ions effectively counteracted lauric acid only. A physicochemical explanation for the relative activities has been attempted.     

Fatty acid uptake and metabolism in a human intestinal cell line (Caco-2): comparison of apical and basolateral incubation

Free fatty acids can enter the enterocyte via the apical or basolateral plasma membrane. We have used the Caco-2 intestinal cell line to examine the polarity of free fatty acid uptake and metabolism in the enterocyte. Differentiated Caco-2 cells form polarized monolayers with tight junctions, and express the small intestine-specific enzymes sucrase and alkaline phosphatase. Cells were grown on permeable polycarbonate Transwell filters, thus allowing separate access to the apical and basolateral compartments. Total uptake of [3H]palmitate bound to bovine serum albumin (palmitate-BSA 4:1) was twofold higher (P less than 0.05 or less) at the apical surface than at the basolateral surface. The relative apical and basolateral membrane surface areas of the Caco-2 cells, as measured by partition of the fluorophore trimethylammonium-diphenylhexatriene TMA-DPH), was found to be 1:3. Thus, apical fatty acid uptake was sixfold higher than basolateral uptake per unit surface area. Analysis of metabolites after incubation with submicellar concentrations of [3H]palmitate showed that the triacylglycerol to phospholipid (TG:PL) ratio was higher for fatty acid added to the apical as compared to the basolateral compartment (20% at 60 min, P less than 0.025). Little fatty acid oxidation was observed. Preincubation with albumin-bound palmitate, alone or with monoolein, increased the incorporation of both apical and basolateral free fatty acids into TG. The results suggest that the net uptake of long-chain free fatty acids across the apical plasma membrane is greater than uptake across the basolateral membrane. In addition, a small increase in the TG:PL ratio for apically, compared to basolaterally, added free fatty acids suggests that polarity of metabolism occurs to a limited extent in Caco-2 enterocytes.     

Binding of fatty acids to the uncoupling protein from brown adipose tissue mitochondria

The uncoupling protein 1 (UCP1) is a H(+) carrier which plays a key role in heat generation in brown adipose tissue. The H(+) transport activity of UCP1 is activated by long-chain fatty acids and inhibited by purine nucleotides. While nucleotide binding has been well characterized, the interaction of fatty acid with UCP1 remains unknown. Here I demonstrate the binding of fatty acids by competition with a fluorescent nucleotide probe 2(')-O-dansyl guanosine 5(')-triphosphate (GTP), which has been shown previously to bind at the nucleotide binding site in UCP1. Fatty acids but not their esters competitively inhibit the binding of 2(')-O-dansyl GTP to UCP1. The fatty acid effect was enhanced at higher pH, suggesting the binding of fatty acid anion to UCP1. The inhibition constants K(i) were determined by fluorescence titrations for various fatty acids. Short-chain (C<8) fatty acids display no affinity, whereas medium-chain (C10-14) and unsaturated C18 fatty acids exhibit stronger affinity (K(i)=65 microM, for elaidic acid). This specificity profile agrees with previous functional data obtained in both proteoliposomes and mitochondria, suggesting a possible physiological role of this fatty acid binding site.     

Transmembrane transport of fatty acids in the heart

Summary Although fatty acid uptake by the myocardium is rapid and efficient, the mechanism of their transmembrane transport has been unclear. Fatty acids are presented to the plasma membrane of cardiomyocytes as albumin complexes within the plasma. Since albumin is not taken up by the cells, it was postulated that specific high affinity binding sites at the sarcolemma may mediate the dissociation of fatty acids from the albumin molecules, before they are transported into the cells. In studies with a representative long-chain fatty acid, oleate, it was in fact shown that fatty acids bind with high affinity to isolated plasma membranes of rat heart myocytes revealing a K_D of 42 nM. Moreover, a specific membrane fatty acid-binding protein (MFABP) was isolated from these membranes. It had a molecular weight of 40 kD, an isoelectric point of 9.0, and lacked carbohydrate or lipid components. Binding to a specific membrane protein might represent the first step of a carrier mediated uptake process. Therefore, the uptake kinetics of oleate by isolated rat heart myocytes was determined under conditions where only cellular influx and not metabolism occurred. Uptake revealed saturation kinetics and was temperature dependent which were considered as specific criteria for a facilitated transport mechanism. For evaluation whether uptake is mediated by MFABP, the effect of a monospecific antibody to this protein on cellular influx of oleate was examined. Inhibition of uptake of fatty acids but not of glucose by the antibody to MFABP indicated the physiologic significance of this protein as transmembrane carrier in the cellular uptake process of fatty acids. Such a transporter might represent an important site for the metabolic regulation of fatty acid influx into the myocardium.     

Critical temperatures for the interaction of free fatty acids with the erythrocyte membrane

Non-esterified long-chain fatty acids reduce the extent of hypotonic hemolysis at a certain low concentration range but cause hemolysis at higher concentrations. This biphasic behavior was investigated at different temperatures (0-37 degrees C) for lauric (12:0), myristic (14:0), palmitoleic (16:1), oleic (cis-18:1) and elaidic (trans-18:1) acids. The results are summarized as follows: (A) the fatty acids examined exhibit a high degree of specificity in their thermotropic behavior; (B) oleic acid protects against hypotonic hemolysis even at the highest concentrations, up to 15 degrees C, when it becomes hemolytic, but only in a limited concentration range; (C) elaidic acid does not affect the osmotic stability of erythrocytes up to 20 degrees C, when it starts protecting: above 30 degrees C, it becomes hemolytic at the highest concentrations; (D) palmitoleic acid is an excellent protecting agent at all temperatures in a certain concentration range, becoming hemolytic at higher concentrations; (E) lauric acid protects up to 30 degrees C and becomes hemolytic only above this temperature; (F) myristic acid exhibits an extremely unusual behavior at 30 and 37 degrees C by having alternating concentration ranges of protecting and hemolytic effects; (G) there is a common critical temperature for hemolysis at 30 degrees C for saturated and trans-unsaturated fatty acids; (H) the initial slope of Arrhenius plots of percent hemolysis at the concentration of maximum protection is negative for cis-unsaturated fatty acids and positive for saturated and trans-unsaturated fatty acids.     

Biosynthesis of Long-Chain Alcohols by Developing and Regenerating Rat Sciatic Nerve

Abstract: Cell-free preparations of rat sciatic nerve were found to catalyze the reduction of fatty acid to alcohol in the presence of NADPH as reducing cofactor. The reductase was membrane-bound and associated primarily with the microsomal fraction. When fatty acid was the substrate, ATP, coenzyme A (CoA), and Mg²⁺ were required, indicating the formation of acyl CoA prior to reduction. When acyl CoA was used as substrate, the presence of albumin was required to inhibit acyl CoA hydro-lase activity. Fatty acid reductase activity was highest with palmitic and stearic acids, and somewhat lower with lauric and myristic acids. It was inhibited by sulfhydryl reagents, indicating the participation of thiol groups in the reduction. Only traces of long-chain aldehyde could be detected or trapped as semicarbazone. Fatty acid reductase activity in rat sciatic nerve was highest between the second and tenth days after birth and decreased substantially thereafter. Microsomal preparations of sciatic nerve from 10-day-old rats exhibited about four times higher fatty acid reductase activity than brain or spinal cord microsomes from the same animals. Wallerian degeneration and regeneration of adult rat sciatic nerve resulted in enhanced fatty acid reductase activity, which reached a maximum at about 12 days after crush injury.