The activation of tryptophanase apo-enzyme by potassium, ammonium and rubidium ions

Abstract

Apo-tryptophanase is activated by NH4, K and Rb ions in the presence of pyridoxal phosphate. Activation occurs at concentrations between 0.001[image] and 0.07[image]. The dissociation of pyridoxal phosphate from the tryptophanase complex occurs only slowly if it is dialyzed against 0.25[image] KCl, but is rapid if dialysis is made against distilled water or 0.25[image] NaCl. KCl and (NH4)2SO4 exert a stabilizing action on tryptophanase. It is suggested that K, NH4 and Rb ions play an important part in the structure of the holo-enzyme. The known effect of K ions on the inhibition of indole production by Escherichia coli grown on glucose-bouillon is discussed.