Synthesis of Fatty Acids by Mitochondria

Abstract

Recent evidence (l-3) shows that the synthesis of long chain fatty acids (mainly palmitic acid) from acetyl coenzyme A (CoA) in the presence of adenosine triphosphate, Mn++, HC03-, and reduced triphosphopyridine nucleotide, is catalyzed by a soluble enzyme system derived from livers.The enzyme system was purified by Gibson et al. (2) and Wakil and Ganguly (4) and the reaction was subfractionated into two distinct fractions.The first fraction (known as acetyl-CoA carboxylase) catalyzes the formation of malonyl-CoA by carboxylating acetyl-CoA in the presence of adenosine triphosphate, Mn++, whereas the second fraction (Rt,J catalyzes the conversion of malonyl-CoA to palmitate in the presence of reduced triphosphopyridine nucleotide.The reaction mixture contained 34.5 mpmoles acetyl-CoA-l-Cl4 (55,200 c.p.m.) 2 pmoles ATP, 0.25 rmole TPNH, 0.25 pmole DPNH, 2.8 mg of mitochondrial protein, 50 pmoles phosphate (pH 6.5), and Hz0 to a total volume of 0.5 ml.Four pmoles KHCOa and 30 mpmoles malonyl-CoA (HOOCCH&140-CoA, 70,000 c.p.m.) were used where indicated.The reaction mixture was incubated anaerobically at 38" for 1 hour.