Stimulation by glutamine of the formation of N6-hydroxylysine in a cell-free extract from aerobacter aerogenes 62-1

Glutamine may serve as an activator and/or regulator of the N⁶-hydroxylase (E.C. 1.14.99) of Aerobacter aerogenes 62-1. Activation and stabilization of N⁶-hydroxylase activity was observed both in vivo and in vitro. Growth in a glutamine-supplemented medium resulted in (1) maximum N⁶-hydroxylase activity at an earlier stage of growth and (2) higher N⁶-hydroxylase activity and continued aerobactin synthesis into stationary phase. Storage of P2 in the presence of L-glutamine (1 mM) significantly increased the lifetime of the labile N⁶-hydroxylase activity. Inclusion of L-glutamine in the incubation mixture typically resulted in a 2-3-fold activation of the hydroxylase activity. The stimulatory effect of glutamine was independent of and additive to the enhancement of N⁶-hydroxylation by the active component(s) in the supernatant, S2 fraction. Glutamic acid-γ-semihydrazide activated slightly in the absence of glutamine but activation of the system by glutamine was decreased by this compound. Azaserine was shown to be an uncompetitive inhibitor with respect to lysine and this inhibition was not reversed by glutamine.