PURIFICATION AND CHARACTERIZATION OF THE ACETATE FORMING ENZYME, ACETYL-COA SYNTHETASE (ADP-FORMING) FROM THE AMITOCHONDRIATE PROTIST, GIARDIA-LAMBLIA

Giardia lamblia, an amitochondriate eukaryote, contains acetyl-CoA syn thetase (ADP-forming), an enzyme known only from one other eukaryote ( Entamoeba histolytica) and a few anaerobic prokaryotes. The enzyme has been purified about 350-fold. The activity in the direction of acetat e formation was dependent on ADP and inorganic phosphate. The reverse reaction could not be detected. Succinyl-CoA, propionyl-CoA and dADP w ere utilized with lower efficiency. The enzyme did not utilize AMP plu s PPi thus differs from the broadly distributed acetyl-CoA synthetase (AMP-forming), The enzyme is responsible for acetate production accomp anied by ATP generation, thus plays an important role in G. lamblia me tabolism.