Acylation of proteins: recent advances.

The biochemistry and cell biology of covalent attachment of the fatty acids palmitic and myristic to proteins has been the subject of extensive investigations during the past fifteen years. While the site of attachment of fatty acids and the primary structure of proteins around the acylation site have been extensively documented, the exact role of the fatty acids have only been speculated upon. Since fatty acids would prefer to be associated with the lipid bilayer of membranes, it has been assumed that the role of the fatty acid is to provide a stable membrane anchor. This review discusses recent reports in the area of fatty acylation which suggests roles for the fatty acid other than that of a stable membrane anchor.

Effect of ethanol on glycerolipid and faty acid metabolism in Hep G2 human-hepatoma cells

It is well-known that ethanol alters fatty acid and glycerolipid metabolism in liver, but most of the studies have been deleloped on rats, so little known about the corresponding effects on human liver. We have chosen the Hep G2 human hepatoma cell line, which appears be an excellent in vitro model system. Cells were incubated in ethanol containing medium (0-400 mM) for 48 h. Incorporation and metabolism of radioactive substrates (14C(U) glycerol, [1-(14)C] palmitic acid and [1-(14)C] eicosatrienoic acid (n-6) were analyzed in cellular and conditioned medium lipids. Cellular growth rate and lipid composition of control and ethanol-treated cells were also studied. The results showed that ethanol inhibited logarithmic cellular growth rate in a concentration dependent manner, without affecting viability. Ethanol (400 mM) did not modify cellular major lipid composition except for an increase of cholesteryl esters, but produced a decrease in the proportions of myristic, palmitic and palmitoleic acids. Ethanol enchanced the incorporation of radioactive fatty acids into cellular glycerolipids but did not alter the rate of incorporation of 14C(U) glycerol. This was attributed to an isotopic solution of the radioactive glycerol as a result of increasde alfa-glycerophosphate biosynthesis. Incorporation of radioactive fatty acids and glycerol into conditioned medium glycerolipids were increased in cells incubated in presence of ethanol. The increased incorporation of 14C glycerol into conditioned medium together with a simultaneous diminuition in labeling cellular glycerides suggest that there would be a simulation of the export of these lipid classes to conditioned medium. Conversion of [1-(14)C] palmitic to oleic acid and eicosatrienoic to arachidonic acid were inhibited in 400 mM ethanol treated cells suggesting an inhibition of delta 9 and delta 5 desaturase activity.

Comparative analysis of erythrocyte fatty acid composition in a sample of Mexico city children and young adults on a free diet

In the present study the influence of age on red blood cell fatty acid (RBCFA) composition was analyzed in a sample of Mexico City children and young people on a free diet, as there is scarce information about RBCFA composition in the Mexican population. Erythrocyte lipids were extracted with isopropyl alcohol and fatty acid methyl esters were prepared to be analyzed by gas liquid chromatography. The 1. to 2-year-old group showed a higher percent level of C18:0 (34.73 ñ 2.5 vs. 29.67 ñ 1.3, p<0.002) and lower of C16:1 (0.58 ñ 0.2 vs. 1.09 ñ 0.2, p<0.005), C20:4 (14.08 ñ 4.1 vs, 18.20 ñ 1.2, p<0.05) and C22:5 (2.79 ñ 1.7 vs. 7.68 ñ 0.8, p<0.001) than the 20- to 25-year-old group. Both groups showed a very low linoleic acid proportion, children 0.48 percent and young adults 0.54 percent. The unsaturated/saturated fatty acid ratio was found to be 0.55 ñ 0.2 in children and 0.91 ñ 0.1 in adults (p<0.001). These findigs indicate the presence of factors related to age that affect the fatty acid composition in the erythrocyte membrane different from diet habits in the sample analyzed. Results are compared with reports in the literature

Los ácidos grasos esenciales y sus funciones / Essential fatty acids and their functions

Se realizó una recopilación sobre los ácidos grasos esenciales y su función en animales y en humanos. La composición de las series n-6, n-3, n-9 y n-7 fue descripta enfatizando la reacción de competición de las mismas, así como también las necesidades diarias de los ácidos n-6 y n-3 en humanos. También se señaló el mecanismo de inter-conversión de los distintos ácidos grasos esenciales. La contribución de las 5 y 6 desaturasas a la formación de los ácidos polinosaturados se ha comentado cuidadosamente, indicándose que nuevos trabajos descartarían la existencia de la 4 desaturasa. A su vez se detalla la estructura del sistema desaturante, su ubicación en el cuerpo del animal y su regulación por medio de factores dietarios y hormonales. Se comentaron la reacciones de elongación y retroconversión, así como también la formación de eicosanoides. La importancia de los ácidos grasos esenciales y sus productos de transformación en la bioquímica clínica se ha tratado detalladamente, focalizando el efecto sobre la epidermis, sistemas cardiovascular y reproductor, presión arterial, diabetes y cáncer

11-Deoxycorticosterone, an inducer of a factor stimulating delta 9 desaturase activity in liver microsomes

Se estudió el efecto de la 11-desoxicorticosterona sobre la desaturación oxidativa del ácido palmítico en microsomas hepáticos de rata. La hormona incrementó en microsomas hepáticos de rata. La hormona incrementó significativamente la actividad de delta 9 desaturasa 24 h después de la inyección intraperitoneal (1 * mol/Kg peso). De la solución de lavado de microsomas hepáticos de animales tratados con hormona se obtuvo un factor proteico que, agregado a suspensiones microsomales de animales controles, fue capaz de reproducir el efecto estimulatorio sobre la delta 9 desaturasa. El factor inducido por tratamiento con desoxicorticosterona se encontró también en el citosol hepático de ratas tratadas con la hormona. Los resultados demuestran que la presencia de un hidroxilo en posición 11-ß, característico de hormonas esteroides con acción glucocorticoide, no es imprescindible para la inducción del factor proteico que regula la actividad delta 9 desaturante