Lipogenesis in particle-free extracts of rat liver. I. Substrates and cofactor requirements.

A particle-free extract has been prepared from rat liver which is capable of incorporating isotopic acetate, pyruvate, and acetyl CoAl into long chain fatty acids. While both cytoplasmic and mitochondrial enzymes are necessary for the complete system, evidence is presented suggesting that the presence of electrolyt,es in the homogenizing medium may act to extract the lipogenic enzymes of the mitochondria into the soluble part,iclefree phase. The coenzyme requirements of this system have been established. In addition, a marked stimulation by cupric ion and by several acids of the tricarboxylic acid cycle has been observed. Some evidence is presented as to the mode of action of the latter.