Whole cells and cell-free extracts of Aerobacter aerogenes possess an enzyme system which actively ammoniates alpha-ketoglutarate The enzyme was obtained in cell-free solution; its action was similar to that in resting cells or growing cells;The concentration of glutamate formed by growing cells in the aerobic dissimilation of a carbon source in higher than that formed under anaerobic conditions. The same is not true far long dialyzed juices where more glutamate is formed anaerobically;The enzyme(s) participating in the ammoniation of alpha-ketoglutarate may be located near the surface of the cell;Short time experiments employing N15 have shown aspartate as a possible product of ammoniation;Alanine and aspartate are formed in high concentra-tion as products of anaerobic dissimilation of a substrate;Reductive ammoniation of pyruvate was not shown. Pyruvate is involved in the synthesis of aspartate because of its role in carbon dioxide fixation. Pyruvate is also significant in the formation of glutamate. A C2 + C3 condensation has been suggested to be followed by ammoniation of a resulting five-carbon compound;Sodium fluoride inhibits ammoniation in dialyzed juices; the inhibition can be relieved by manganous sulfate. Sodium arsenite and methadon hydrochloride accentuate the formation of alanine and to a lesser degree that of aspartate and glutamate.