Biosynthesis of fatty acids in cell-free preparations. 5. Synthesis of fatty acids from acetate in extracts of lactating-rat mammary gland

The investigations of Folley & PopjAk and their colleagues demonstrated the outstanding ability of the mammary gland of lactating animals to synthesize fatty acids from acetate (for reviews see Popjfik, 1952; Folley & McNaught, 1961). Investigations on whole animals or on tissue slices could not establish the nature of the intermediates involved, although the overall process was shown to be analogous or equivalent to the reversal of ,-oxidation of fatty acids (Popjak, French, Hunter & Martin, 1951). Popjak & Tietz (1954, 1955), Tietz & Popjak (1955) and Hele, Popjfik & Lauryssens (1957) made an attempt to elucidate this process in cell-free preparations of mammary gland and have shown that CoA, ATP and a reduced pyridine nucleotide were essential co- factors. Investigations on the mechanisms of fatty acid oxidation with cell-free enzyme systems and purified enzymes led to the suggestion that the biosynthesis of fatty acids occurred by the reversal of this process (Lynen & Ochoa, 1953; Seubert, Greull & Lynen, 1957; Langdon, 1957). The ex- perimental data of Hele et al. (1957) obtained with fractions of soluble extracts of lactating-rabbit mammary gland were also interpreted so as to support this idea.