Enzymatic transfer and hydrolysis involving glutamine and asparagine.

The occurrence in bacteria of transferases, enzymes which catalyze the exchange of the p-aspartyl group of asparagine and the r-glutamyl group of glutamine with hydroxylamine or labeled ammonia, has been described (14). Transferase activities have also been found in extracts of mammalian tissues (5), in the mold Neurospora crassa,l and in extracts of green plants (6-8). Whereas transferase activity in plant (7), mammalian (5), and Neurospora preparations’ is dependent upon the presence of manganese together with phosphate or arsenate, these ions do not appear to be necessary for transferase activity in bacterial preparations (2). Recently, however, purified preparations of Proteus vulgaris were also found to possess a second type of glutamotransferase which is activated by manganese (9). Transfer reactions leading to the synthesis of glutamyl peptides from glutamine were catalyzed by preparations of Bacillus subtilis (10). As in the case of the bacterial transferases, the synthesis of glutamyl peptides by B. subtilis does not require the presence of any cofactors. Enzymes called synthetases, which catalyze the synthesis of glutamine or glutamohydroxamic acid from glutamic acid and either ammonia or hydroxylamine, were found in animal (11-13)) plant (14, 15), and microbial (16, 17) systems. A similar system in lupine seedlings, which synthesizes asparagine from aspartic acid and ammonia, has recently been described (18). Synthetase activities require the presence of ATP2 and magnesium ions. Enzymes were also found which catalyze the hydrolysis of glutamoand aspartohydroxamic acids (2, 19). The relationship among the various enzymatic reactions mentioned above is not clear. It would be of great interest to ascertain whether all the four reactions, (1) the synthesis of the amide, (2) the hydrolysis of the amide, (3) the transfer reactions leading to the formation of the corresponding hydroxamic acids, and (4) the hydrolysis of the hydroxamates, are due to the activity of one enzymatic system or whether several enzyme