AN AROMATIC AMINO ACID TRANSAMINASE FROM MUNG BEAN

A transaminase has been isolated and purified from young mung bean plants (Phaseolus aureus Roxb.). The enzyme catalyzes the transamination of phenylalanine in the presence of α-ketoglutarate with the production of equimolar amounts of phenylpyruvate and glutamate. Tyrosine and tryptophan also serve as substrates, and relative rate measurements indicate that only one enzyme is involved. In addition to α-ketoglutarate the enzyme also utilizes pyruvate, and to some extent glyoxylate and oxaloacetate as amino acceptors. The enzyme is stable in solution at 0–4 °C for several weeks, and acetone powders of the young plants stored at 0–4 °C retained their activity for several months. The enzyme is inhibited by precipitation with ammonium sulphate, and the activity is lost after freezing.