RESUMO
Cell-free extracts of some actinomycetes were found to contain some transaminases enzymes. Streptomyces nitrosporeus was selected as the most inducer for L-alanine-glycine and L-alanine glutamate transaminases. The first enzyme catalyzes the formation of pyruvate and lycine from L-alanine and glyoxylate, while the second enzyme catalyzes the formation of pyruvate and L-glutamate from L-alanine and alpha-ketoglutarate. The reversibility of the two reactions was demonstrated. The optimum activity of the first enzyme occurred at pH 7.5, while that of the second enzyme occurred at pH 8.0. The optimum temperature of the two enzymes was 40C. The temperature activity profiles and heat inactivation kinetics of the two enzymes were different, so the two reactions seem catalyzing by two different enzymes. The Km values for all substrate were calculated. The activity of the two enzymes was stimulated by the addition of pyridoxal phosphate, and was inhibited by the addition of hydroxylamine. The inhibition by hydroxylamine was overcome by pyridoxal phosphate. Stability of the two enzymes was studied. Dialysis for 24 hours against 0.02 M phosphate buffer pH 8.0, completely inhibited the activity of the two enzymes