Oxygen-dependent inactivation of glutamine phosphoribosylpyrophosphate amidotransferase in vitro inactivation

Abstract

The oxygen-dependent inactivation of glutamine phosphoribosylpyrophosphate amidotransferase (ATase) is demonstrated in cell extracts of Bacillus subtilis. The rate of inactivation of ATase in vitro is apparently first order with respect to oxygen concentration and ATase activity. ATase inactivation in vitro (or in vivo) cannot be reactivated by a variety of reductants. ATase is significantly stabilized to oxygen-dependent inactivation in vitro in the presence of tetrasodium phosphoribosylpyrophosphate and glutamine together. The effects of the end product inhibitors, adenosine 5-monophosphate (AMP) and guanosine 5-monophosphate (GMP), on the stability of ATase are antagonistic. AMP stabilizes ATase, whereas GMP destabilizes the enzyme. The stability of ATase can be manipulated over wide ranges by variations in the AMP/GM ratio. The effects of AMP and GMP on the inactivation of ATase in vitro are very specific. ATase is partially inhibited by 1,10-phenanthroline, suggesting that the enzyme contains iron (or some other chelatable metal ion). The inactivation of ATase in vitro is proposed to present a model for the reconstruction of the inactivation of ATase in stationary-phase cells of B. subtilis.