The Formation of Ammonia in Brain Extracts

The phosphofructokinase reaction proceeds in an autocatalytic manner when Na+ and Mg++ are the only cations present in a system containing an extract of powdered, acetone-dried dog brain.The addition of NHf or Kf will abolish the induction period.Since NH,+ stimulates the reaction so markedly in crude extracts (1) and also in purified enzyme preparations (2), whereas K+ does not stimulate in purified preparations, there was a possibility that NH4t-was being produced while the phosphofructokina,se reaction was proceeding and thus produced the autocat.alyticeffect.Analysis of the reaction mixture at the time interval during which the greatest increase in reaction velocity occurred showed that a considerable amount of NH*+ had been formed.It was found that the NH4+ was formed from AMP-5* and that ATP was necessary for its rapid production, but no inorganic phosphate or inorganic pyrophosphate is liberated concomitantly with the NH,+.The enzyme or enzyme system is different from AMP-5 deaminases which have been previously described.EXPERIMENTAL