MECHANISTIC STUDIES ON NITROGENASE FROM KLEBSIELLA PNEUMONIAE USING THE RAPID QUENCH TECHNIQUE

Abstract

ABSTRACT A mechanism for the nitrogenase-catalysed reduction of dinitrogen (N2) to ammonia is presented. The mechanism is based on pre-steady state kinetic data for dihydrogen (H2), hydrazine (N2H4) and ammonia (NH3) formation obtained by a rapid quench technique and on a consideration of the chemistry of transition metal dinitrogen, dinitrogen hydride and hydride complexes. Stopped-flow spectrophotometry has demonstrated that electron transfer between the component proteins of nitrogenase is coupled to the hydrolysis of MgATP and that the dissociation of the oxidised Fe protein from reduced Mo-Fe protein is the rate limiting step in the catalytic cycle. A hydrazido(2–) species is suggested as an intermediate in N2 reduction and a nitride or nitrene species as an intermediate in both N2 and azide reduction.