Ammonia formation in brain. 2. Brain adenylic deaminase

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Abstract
Adenylic deaminase of ox brain was purified 10- to 20-fold by fractionating the aqueous extract of acetone powder with ammonium sulfate and alumina gel C [gamma]. The activity is associated with insoluble particles which can be separated on the high-speed centrifuge. Treatment with sodium cholate, though inhibitory, produces some solubilization, as shown by the appearance of activity in the supernatant solution. Under standard conditions the preparation is practically free of adenosinetri-phosphatase, 5-nucleotidase, myokinase and adenosine deaminase activities. The activity of the enzyme is greatly increased by adenosine triphosphate (ATP). The effect is specific; adenosine diphosphate, inosine tri- and di- phosphates are inactive. Some activity persists even in complete absence of ATP. This activity cannot be accounted for by adenosine deaminase action. The effect of varying ATP concentrations on the activity of the enzyme is independent of the concentration of adenylic acid. The pH optimum is 6.2-6.8. The enzyme is inhibited by some multivalent cations and by fluoride. Other inhibitors were tested. ATP is recovered unchanged at the end of the reaction, while adenylic acid is converted into inosinic acid and ammonia.