RESUMEN
1. Hepatocytes were isolated by perfusion of the liver with collagenase/salt solutions and incubated in culture after attachment to plastic culture dishes for periods up to 48 h. 2. The cells, when incubated in serum-free culture medium in the presence of insulin, showed enhanced stearolyl-CoA desaturase activity which was not observed when 50 muM cycloheximide was included. When insulin was omitted from the medium, the cells lost 80% of their original desaturase activity. 3. Cells isolated from animals fed 20% (w/w) sucrose for two weeks prior to sacrifice, showed high levels of fatty acid synthesis, stearolyl-CoA desaturase activity and triacylglycerol synthesis when compared with cells isolated from animals fed a corn oil supplemental diet. 4. The observations are discussed in terms of the influence of stearoyl-CoA desaturase activity on hepatic lipogenesis.
Asunto(s)
Ácido Graso Desaturasas/metabolismo , Lípidos/biosíntesis , Hígado/metabolismo , Estearoil-CoA Desaturasa/metabolismo , Acetatos/metabolismo , Animales , Carbohidratos de la Dieta , Grasas de la Dieta , Inducción Enzimática , Ácidos Grasos/metabolismo , Técnicas In Vitro , Cinética , Ácidos Linoleicos/farmacología , Hígado/efectos de los fármacos , Masculino , Aceites , Ratas , Ácidos Esteáricos/metabolismo , Sacarosa/farmacología , Triglicéridos/metabolismoRESUMEN
The interaction of rat mammary gland medium-chain thioesterase with yeast fatty acid synthetase has been investigated. Medium-chain thioesterase interacts with yeast fatty acid synthetase causing premature chain termination of the fatty acids synthesized from acetyl-CoA and malonyl-CoA. This effect is most marked under conditions of rate-limiting malonyl-CoA availability. Immobilized yeast fatty acid synthetase specifically binds rat mammary gland medium-chain thioesterase. This interaction has been used to purify medium-chain thioesterase to near homogeneity from samples of rat mammary gland cytosol. The stoichiometry of binding of medium-chain thioesterase to yeast fatty acid synthetase has been investigated. Yeast fatty acid synthetase binds 5.7 +/- 1 mol medium-chain thioesterase/mol yeast fatty acid synthetase. It is concluded that yeast fatty acid synthetase has a medium-chain thioesterase binding site.