Animal fatty acid synthetase. A novel arrangement of the beta-ketoacyl synthetase sites comprising domains of the two subunits.

Chicken Liver Fatty Acid Synthetase-The enzyme was prepared and assayed as described previously (7) and had a specific activity of 1200 nmol of NADPH oxidized min-mg-'.The protein concentration was estimated from the dry weight-A28o relationship (7).1,3-Dibromo-2-propanone-The dibromopropanone (Eastman) was purified as described previously (8).The 1,3-dibromo-2-[2-'4C]propanone (1.79 Ci/mol) was prepared according to the procedure of Lowe (4) and will be described elsewhere.Chemicals-Buffers were prepared from Baker reagent grade salts.Acetyl-and malonyl-CoA were obtained from P-L Biochemicals.Consistently, both commercial reagents contained about 0.1 mol % CoA and the malonyl-CoA preparation contained 5 mol % acetyl-CoA as contaminants.The acyl-CoA preparations were freed of CoA and the malonyl-CoA was freed of acetyl-CoA by high pressure liquid chromatography on a C-18 reverse phase Custom LC Customsphere 5128