Phosphotransacetylase from Clostridium acidiurici

The phosphotransacetylase from Clostridium acidiurici has two properties not observed for this enzyme in other bacteria: (i) it requires a divalent metal for activity, and (ii) it is not subject to uncoupling by arsenate. The enzyme has been obtained in highly purified form, with a specific activity 500-fold higher than crude extracts. Ferrous or manganous ions are required for maximal activity, with Mn(2+) being 50 to 75% as effective as Fe(2+). The acetyl group can be transferred from acetyl phosphate to coenzyme A in 20 mm arsenate without a net decrease in high-energy acyl linkages. Likewise, H(32)PO(4) (2-) will exchange with acetyl-PO(4) (2-) in the presence of arsenate without loss of acetyl phosphate. This suggests that the active site on the enzyme is capable of discriminating between phosphate and arsenate while permitting the reversible transfer of acyl groups between CoA and phosphate.