Purification and role of phosphotransbutyrylase.

In recent years acyl phosphates have received much attention. For example, acetyl (1, 2), propionyl (3, 4), butyryl (5, 6), carbamyl (7, 8), and aspartyl (9) phosphates have been studied in detail. In fermentative bacteria the role of phosphotransacetylase, which facilitates an interconversion of acetyl phosphate and acetyl coenzyme A has been well documented (1,2,10-12). An enzyme capable of catalyzing the direct transfer of the butyryl moiety of butyryl coenzyme A to inorganic phosphate has been found in extracts of Clostridium butyricum. The purified enzyme carries out a rapid arsenolysis of butyryl phosphate but not of acetyl phosphate. Cleavage of butyryl phosphate is dependent upon enzyme, arsenate, and coenzyme A. These properties are pertinent to the classification of this enzyme with the phosphotransacetylases found in many anaerobic bacteria. The specificity of the enzyme for butyryl phosphate marks its importance in the energy metabolism of the butyric clostridia. The following mechanism for the conversion of the thiol ester bond energy of butyryl coenzyme A to the adenylic acid system has been discussed (13) :