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At least 289 records · Page 16Linked to original sources
PubMed1978

Distribution of radioactivity in myelin lipids following subcutaneous injection of [14C]stearate.

Blood fatty acids are an important parameter for the synthesis of brain myelin as exogenous stearic acid is needed: after subcutaneous injection to 18-day-old mice this labelled stearic acid is transported into brain myelin and incorporated into its lipids. However the acid is partly metabolized in the brain by elongation (thus providing very long chain fatty acids, mainly lignoceric acid) or by degradation to acetate units (utilized for synthesis of medium chain fatty acids as palmitic acid, and cholesterol). These metabolites are further incorporated into myelin lipids. The myelin lipid radioactivity increases up to 3 days; most of the activity is found in phospholipids; their fatty acids are labelled in saturated as well as in polyunsaturated homologues but sphingolipids, especially cerebrosides, contain also large amounts of radioactivity (which is mainly found in very long chain fatty acids, almost all in lignoceric acid). The occurrence of unesterified fatty acids must be pointed out, these molecules unlike other lipids, are found in constant amount (expressed in radioactivity per mg myelin lipid).

Animals↗
PubMed1983

Sepharose-stearate as substrate for rat liver long-chain fatty acyl-CoA synthetase.

Stearic acid coupled covalently to Sepharose 6B serves as substrate for thioesterification catalyzed by rat liver long-chain fatty acyl-CoA synthetase (ATP-forming) (EC 6.2.1.3). Availability as substrate is dependent upon the conservation of the free omega-terminal in addition to that of the free carboxyl function. The enzymatic overall formation of matrix-acyl-CoA in the presence of ATP and CoA as cosubstrates conforms to the stoichiometry reported for thioesterification of the free long-chain fatty acyl substrate. The preformed matrix-acyl-CoA serves as substrate for the backward synthetase reaction in the presence of AMP and PPi. The apparent Km values for ATP and CoA in the presence of the acyl matrix are similar to the respective Km values observed in the presence of the free acid substrate. The apparent Km for the acyl matrix is 10-fold higher (0.5 mM) than the apparent Km value for the free acid. The feasibility of enzymatic thioesterification of bound long-chain fatty acids implies that the exact nature of the bulky chain situated between the carboxy and omega-terminal plays a secondary role in defining the fatty acyl substrate specificity for long-chain fatty acyl-CoA synthetase. Also, dissociation of bound long-chain fatty acids does not constitute an obligatory preliminary step to fatty acid thioesterification.

Animals↗
PubMed2006

Chain orientation and headgroup structure in Langmuir monolayers of stearic acid and metal stearate (Ag, Co, Zn, and Pb) studied by infrared reflection-absorption spectroscopy.

The monolayers of stearic acid at the air-water interface on pure water and ion-containing subphases have been studied using infrared reflection-absorption spectroscopy. In the presence of Co(2+), Zn(2+), and Pb(2+), ordered hydrocarbon chains and hexagonal subcell structure remain almost unchanged in comparison with those for the monolayer on pure water at the surface pressure of 20 m/Nm. In the cases of Co(2+) and Zn(2+), the H-bonded monodentate and unsymmetric bidentate chelating structure within the headgroups were formed, and in the case of Pb(2+), three types of structures, bidentate chelating, unsymmetric chelating, and bidentate bridging coordinations, were formed. The hydrocarbon chains in the monolayers are uniaxially oriented at a tilt angle of approximately 0 degrees with respect to the surface normal in contrast to a tilt angle of approximately 20 degrees on pure water surface at 20 m/Nm by the computer simulation of theoretical calculation to experimental data. In the presence of Ag(+), multilayers were developed with the highly ordered hydrocarbon chains in a triclinic subcell structure and a bidentate bridging structure within the headgroups. The multilayers were composed of three monolayers and the hydrocarbon chains in each monolayer were oriented at an angle of approximately 30 degrees away from the surface normal with their C-C-C planes almost perpendicular to the water surface.

Journal Article↗
PubMed1995

Fatty acylation of the rat asialoglycoprotein receptor. The three subunits from active receptors contain covalently bound palmitate and stearate.

Rat hepatic asialoglycoprotein receptors (ASGP-Rs) are hetero-oligomers composed of three homologous glycoprotein subunits, designated rat hepatic lectins (RHL) 1, 2, and 3. ASGP-Rs mediate the endocytosis and degradation of circulating glycoconjugates containing terminal N-acetylgalactosamine or galactose, including desialylated plasma glycoproteins. We have shown in permeable rat hepatocytes that the ligand binding activity of one subpopulation of receptors (designated State 2 ASGP-Rs) can be decreased or increased, respectively, by ATP and palmitoyl-CoA (Weigel, P. H., and Oka, J. A. (1993) J. Biol. Chem. 268, 27186-27190). We proposed that a reversible and cyclic acylation/deacylation process may regulate ASGP-R activity during endocytosis, receptor-ligand dissociation, and receptor recycling. In the accompanying paper (Zeng, F-Y., and Weigel, P. H. (1995) J. Biol. Chem. 270, 21388-21395), we show that the ligand binding activity of affinity-purified State 2 ASGP-Rs is decreased by treatment with hydroxylamine under mild conditions consistent with these ASGP-Rs being fatty acylated in vivo. In this study, we used a chemical method to determine the presence of covalently-bound fatty acids in individual ASGP-R subunits. The affinity-purified ASGP-R preparations were separated by SDS-polyacrylamide gel electrophoresis under nonreducing conditions, and the gel slices containing individual RHL subunits were treated with alkali to release covalently bound fatty acids, which were subsequently analyzed by gas chromatography and confirmed by gas chromatography-mass spectrometry. Both stearic and palmitic acids were detected in all three receptor subunits. Pretreatment of ASGP-Rs with hydroxylamine before SDS-polyacrylamide gel electrophoresis reduced the content of both fatty acids by 66-80%, indicating that most of these fatty acids are attached to cysteine residues via thioester linkages. Furthermore, when freshly isolated hepatocytes were cultured in the presence of [3H]palmitate, all three RHL subunits in affinity-purified ASGP-Rs were metabolically labeled. We conclude that RHL1, RHL2, and RHL3 are modified by fatty acylation in intact cells.

Acylation↗