Fatty acid biosynthesis: II. Fate of fatty acids synthesised by subcellular fractions of lactating-rabbit mammary gland

Abstract

1. 1. Subcellular fractions of lactating-rabbit mammary gland have been incubated under optimum conditions for fatty acid synthesis and the nature and subcellular site of the products examined. 2. 2. When “microsomal + particle-free supernatant” fractions were incubated with labelled acetate, a large proportion of the radioactivity was associated with newly synthesised glycerides in the microsomal fraction. Radioactive unesterified fatty acids were found to be located in the particle-free supernatant. 3. 3. Particle-free supernatant fractions alone synthesised exclusively unesterified fatty acids. 4. 4. Though both the mitochondrial and microsomal fractions bind synthesised fatty acids, the microsomal fraction stimulated both fatty acid and glyceride synthesis to a greater extent than did the mitochondrial fraction. 5. 5. It has been shown that whereas certain free fatty acids inhibited fatty acid synthesis, the corresponding glycerides had little inhibitive effect. 6. 6. The results support the view that the microsomal stimulation of fatty acid synthesis is due, at least in part, to a relief of the feedback inhibition excercised by the products of fatty acid synthesis.