Purification and characterization of a phosphotransacetylase from Rhodopseudomonas palustris

A phosphotransacetylase was purified to apparent homogeneity from photolithoautotrophically grown Rhodopseudomonas palustris by liquid chromatography methods. A 400-fold increase in specific activity could be achieved. The enzyme was characterized by a relative molecular mass of 54,500, an isoelectric point of 6.3 and the absence of dissociable subunits. The enzyme appeared very labile at elevated temperatures or in diluted solutions. The stability could be increased distinctly in case sulfate or ammonium ions were added to the enzyme solution. The activity also was influenced by inorganic salts. Potassium and ammonium ions activated the enzymatic reaction. Sulfate ions revealed an inhibitory influence. A strong substrate inhibition was found with coenzyme A as substrate. The Arrhenius plot revealed a discontinuity at 15 degrees C which most likely corresponds to a conformational change of the enzyme protein.