Sagers, Richard D. (University of Illinois, Urbana), Moshe Benziman, and I. C. Gunsalus. Acetate formation in Clostridium acidiurici: Acetokinase. J. Bacteriol. 82:233-238. 1961.-To define the energy-yielding reaction(s) during fermentation of purines by Clostridium acidi-urici, an eightfold purified acetokinase was obtained by protamine and ammonium sulfate fractionation of crude extracts. Enzyme activity was determined by measuring the disappearance of acetyl phosphate using adenosine diphosphate (ADP) as phosphate acceptor or by following the generation of acetyl phosphate from adenosine triphosphate (ATP) + acetate. The optimal pH for the reaction was observed to be 7.4. K(m) values for acetyl phosphate, ADP, and magnesium ions were shown to be 2.1 x 10(-3)m, 3.2 x 10(-3)m, and 2.4 x 10(-3)m, respectively. Acetyl phosphate disappearance is dependent upon ADP and is stoichiometric with addition of the latter. The acetokinase reaction probably represents the major energy-yielding reaction during purine fermentation by this organism. A pathway for acetate generation from formiminoglycine is proposed, and evidence for a number of enzyme activities intermediate between formiminoglycine degradation and acetate formation is given. The enzyme activities demonstrated are compatible with the over-all purine fermentation rate by whole cells.