Fatty acyl-coenzyme A elongation in brain of normal and quaking mice.

Microsomal enzyme systems from mouse brain that catalyze, respectively, the elongation of palmitoyl-coenzyme A (palmitoyl-CoA), stearoyl-CoA, or arachidyl-CoA appear and reach maximal activity at different times after birth of the animal. A specific C(20)-CoA elongating system exists in mouse brain in addition to the previously recognized C(16)-CoA and C(l8)-CoA elongating enzymes. The C(20)-CoA elongation system is severely reduced in the mutant quaking mouse.

Synthesis of dipalmitoyl lecithin by alveolar macrophages.

A reliable, relatively simple method for isolation and quantification of disaturated lecithins is described. In rabbit lung, 34% of the lecithins were disaturated, in alveolar macrophages, 19%. More than 95% of the fatty acids of the disaturated lecithins from lung and alveolar macrophages was palmitic. Hence, the disaturated lecithins from these sources were essentially all dipalmitoyl lecithin. Both heterophils and alveolar macrophages incorporated (14)C-labeled choline and palmitate into disaturated lecithins. Liver slices in which only about 1% of the lecithins were disaturated incorporated very little of these precursors into this fraction. Of the palmitate incorporated in vitro into disaturated lecithins by alveolar macrophages, heterophils, and lung slices, 37% was in the 1 position. In disaturated lecithins isolated from pulmonary lavage fluid, alveolar macrophages, and lung of rabbit 8-12 hr after a single intravenous injection of palmitic-1-(14)C acid, 45% of the (14)C was in position 1. At earlier times, from 20-240 min after injection, the distribution of (14)C was similar in the samples from lung, but in those from alveolar macrophages and lavage fluid, the percentage in position 1 was slightly lower.Glycerol-U-(14)C was incorporated into disaturated lecithins by alveolar macrophages and by lung slices in vitro. Both tissues incorporated very little label from ethanolamine or from methyl-labeled methionine into this fraction. All of the data are consistent with the view that alveolar macrophages synthesize dipalmitoyl lecithin via the cytidine diphosphate-choline pathway.

Purification and properties of fatty acid synthetase from a human breast cell line.

A human mammary epithelial cell line (SKBr3) has been identified in which fatty acid synthetase constitutes up to 28%, by weight of the cytosolic proteins. The enzymes has been purified to near homogeneity from this cell line and some of its properties studied. In common with fatty acid synthetases from other animal tissues, the enzyme is a 480 000 dalton dimer of similar molecular weight subunits, it synthesizes predominantly palmitic acid and is inactive in the absence of free coenzyme A. The kinetic properties and amino acid composition of the enzyme are also similar to those of fatty acid synthetases from various tissues of other animals. Appreciable structural resemblance between human and rodent fatty acid synthetases is indicated by studies on the immunological cross-reactivities of these enzymes.

Biosynthesis of acyl groups on molecular species of biliary phosphatidylcholines during metabolism of [2,2,2-2H3]ethanol.

Incorporation of deuterium into different positions of individual molecular species of biliary phosphatidylcholines was determined in bile fistula rats given [2,2,2-2H3]ethanol under conditions ensuring maximal rate of oxidation for 24 h. The deuterium-labelling of the glycerol moiety of the major molecular species was about 6-8 atom% at the end of ethanol administration. The deuterium excess at each of the different positions of the glycerol moiety of 1-palmitoyl-2-linoleoyl phosphatidylcholine was less than 3 atom%. From the isotopic composition of the palmitoyl residues of the phosphatidylcholines, it was calculated that [2,2,2-2H3]ethanol supplied about 35-40% of the acetyl-CoA forming the terminal methyl group and about 25-30% of the other C2 units of the palmitic acid chain. This difference in deuterium incorporation was interpreted as being due to an isotope effect, probably in the rate-limiting carboxylation step of acetyl-CoA. Most or perhaps all of the acetyl groups derived from ethanol were introduced into the terminal methyl group without loss of deuterium. This indicates that citrate is not an important carrier of acetyl-CoA in the biosynthesis of fatty acids from ethanol.

Stereoselectivity in the 2-methylbutyrate incorporation into anteiso fatty acids in Bacillus subtilis mutants.

Two Bacillus subtilis mutants defective in branched-chain alpha-ketoacid dehydrogenase can grow when 2-methylbutyrate is provided in trypticase soy medium. Both enantiomers of the acid supported growth of the mutants but the (S)-(+)-isomer (natural) was more active than the (R)-(-)-isomer (unnatural). The mutants utilized these isomers as primer to specifically synthesize either enantiomer of anteiso fatty acids. No racemization of the isomer primers was observed during the synthesis. Thus, cells grown with (-)-isomer possessed anteiso fatty acids (over 80%) of the total fatty acids, being entirely the unnatural enantiomer. The stereospecific synthesis was found to be controlled at the step of 2-methylbutyryl-CoA synthesis. In a wild strain, only (+)-specific acyl-CoA synthetase was detected. In the mutants, either enantiomer of 2-methylbutyrate could simultaneously induce both types, (+)-specific and (-)-specific, of acyl-CoA synthetase. (+)-Specific synthetase had a higher activity and affinity towards substrate than (-)-specific synthetase. The detailed preparative procedures for (R)-(-)- and 2-[3,4-3H]methylbutyric acid are described.

Some characteristics of soluble fatty acid synthesis in germinating pea seeds.

Soluble fractions from germinating pea synthesize palmitic acid de novo and stearic acid by elongation. Malonyl CoA, acyl carrier protein and NADPH are required for both reactions. In contrast to some other plant systems, no requirement was found for divalent cations. On the other hand, the formation of both stearate and palmitate was inhibited by sulphydryl reagents and palmitate elongation was sensitive to arsenite. The products of the reactions were examined and found to be principally acyl-acyl carrier proteins and unesterified fatty acids. Unlike the pea microsomal fractions, the soluble enzymes are stimulated only slightly by the addition of exogenous lipids. The substrate for palmitate elongation is palmitoylacyl carrier protein, which is quantitatively elongated to stearate. Comparisons are made with membrane-localised fatty acid synthesis from the same tissue.

The effects of cerulenin on lipid metabolism in vitro in cellular preparations from the rat.

The effects of the fatty acid-like antibiotic, cerulenin, on fatty acid biosynthesis in preparations of rat adipocytes and mammary cells in vitro have been investigated. Synthesis of palmitic acid was most strongly inhibited, although the magnitude of the effect was dependent on the nature of the tissue, and was especially diminished in the larger adipocytes from older rats. Cerulenin had no effect on the chain-elongation of preformed fatty acids in any of the tissues studied. Some inhibition of the esterification of preformed palmitic acid was also observed, but this appeared to be due to disruption of the cells rather than direct inhibition of the acyltransferases. It is concluded that cerulenin is a valuable experimental tool in studies of lipogenesis in preparations of intact mammalian cells in vitro.

Studies on the biosynthesis of beta-amino acids, the lipid moiety of iturins A, in Bacillus subtilis.

The biosynthesis of the beta-amino acid components of iturins A was studied in comparison to the biosynthesis of fatty acids. Palmitic acid was incorporated into the lipid moiety of iturins A when it was added to the culture medium of the iturin producer Bacillus subtilis. Addition of unlabeled palmitic acid enhanced the formation of straight-chain beta-amino acids and addition of valine or leucine increased the production of branched beta-amino acids. These modifications correlated with modifications in the corresponding biosynthesized fatty acids.

Incorporation of 14C acetate into the phospholipids and fatty acids of rabbit lens in organ culture.

Lenses were cultured in Medium 199 containing 14C acetate for 3, 6, 12 and 20 hours. There was a linear increase in incorporation into the total lipids with time. The total lipid extract was subjected to two-dimensional chromatography and incorporation into the individual classes of lipids was measured. For all time periods approximately 70% of all incorporated radioactivity was seen in the sterol and phosphatidyl choline (PC) fractions. Incorporation was observed in phosphatidyl ethanolamine (PE), aldehydes of PC and PE plasmalogens, phosphatidyl inositol (PI), PC plasmalogens, PE plasmalogens, sphingomyelin (SM), phosphatidic acid (PA) and phosphatidyl serine (PS). The fatty acids of the total lipids were methylated and subjected to gas chromatography, and individual fatty acids were collected. The greatest incorporation occurred in palmitic acid (16:0) and myristic acid (14:0) with minor amounts in lauric acid (12:0). These are the major products of de novo synthesis. The remainder of the radioactivity appeared in fatty acids 18 carbons or longer, which are the products of an elongation mechanism.

[Essential fatty acids: its transformations and functions]. / Los ácidos grasos esenciales: sus transformaciones y funciones.

Essential fatty acids, in animals, pertain to two different fatty acid families: the linoleic and the linolenic. These, and the non-essential families of oleic and palmitoleic are produced by action of the enzymes proper. The lack of essential fatty acids produces typical symptoms that are accompanied by fatty acid compositions, also typical, utilized with diagnostic value. The biological effects of essential fatty acids can be specific and nonspecific. The latter manifest themselves particularly in the phospholipid composition and, therefore, in the structure and fluency of the membranes. In contrast, specific essential fatty acids act in the formation of prostaglandins, prostacyclins, tromboxans and leucotriens. Each essential fatty acid produces specific effects, depending on the prostanoids formed and the tissue in question.

[Formation of primary alcohols and palmitic acid in the microbiological oxidation of hexadecane]. / Obrazovanie pervichnykh spirtov i pal'mitinovoi kisloty pri mikrobiologicheskom okislenii geksadekana

Forty seven microbial strains oxidized hexadecane to form primary cetol and palmitic acid. The maximum quantitiy of the compounds was accumulated in the exponential phase of growing cultures (for 72 hours) and for 6 to 16 hours of incubation of resting cell suspensions. Candida yeast were shown by the gas-liquid chromatography method to be the most active producers of cetol.