Glutamine transaminase from brain tissue. Further studies on kinetic properties and specificity of the enzyme.

Glutamine transaminase, highly purified from rat brain, was studied. In the first series of experiments, the kinetics of the transamination reaction between 2-oxoglutaramate and phenylalanine were examined in order to determine the type of reaction mechanism. This proved to be of the ping-pont type, as can be expected for a transamination. The specificity of the enzyme for various amino acids and 2-oxo acids was then studied in detail. The most active substrates were glutamine, methionine and ethionine as amino-group donors, and phenylpyruvate, glyoxalate and 2-oxo-4-methiobutyrate as amino-group acceptors. For these and several other substrates, the kinetic constants, V and Km, were determined.