Rat Mammary Acetyl Coenzyme A Carboxylase

The isolation of acetyl-CoA carboxylase from lactating rat mammary glands is described. A procedure was used which differs significantly from those employed by others who have isolated this enzyme from animal tissues. The purified enzyme catalyzes the carboxylation of 5.5 pmoles of acetylCoA per min per mg of protein under optimum assay conditions. Apparent K, values were determined for acetyl-CoA, propionyl-CoA, bicarbonate, and ATP (which gave two values). The effects of varying the concentrations of citrate or Mg++ yielded sigmoid saturation curves. Phospholipids were found to stimulate the enzyme.