Fatty acid synthesis in cell-free preparations of rat liver containing phosphorylating mitochondria

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Abstract
A cell-free preparation of rat liver is described in which long-chain fatty acids are synthesized from acetate by way of malonyl-CoA. All the cofactors required for fatty acid synthesis from acetate are derived endogenously from the preparation itself; the ATP and HCO- 3 required for the conversion of acetate into malonyl-CoA are derived entirely from phosphorylating mitochondria. Citrate, isocitrate and malonate do not stimulate fatty acid synthesis in this preparation. The rate-limiting step for fatty acid synthesis in this preparation is the conversion of acetyl-CoA into malonyl-CoA, and the rate at which this takes place is limited by the supply of ATP generated by the mitochondria. For the study of hormonal regulation of fatty acid synthesis in the whole cell this preparation has some advantages over more purified cell-free systems in which exogenous cofactors are added in optimum concentrations.