Characterization of fatty acid synthesis by cow mammary subcellular fractions.

Cellular site of fatty acid synthesis was investigated with mammary tissue from lactating cows. Cytosol, mitochondrial, and microsomal fractions were obtained by differential centrifugation and characterized by measurement of marker enzymes. Two incubation media were utilized to quantitate acetate incorporation into fatty acids by the subcellular fractions. The cytosol fraction synthesized fatty acids from 4 to 16-carbons in chain length with the pattern similar to those synthesized in vivo. No significant acetate incorporation into fatty acids was obtained with mitochondria or microsomal incubations. The malonyl-CoA pathway was the predominant pathway of fatty acid synthesis in cow mammary cytosol as evidenced by inhibitory studies with avidin.