MECHANISM OF Fe++-CYTOCROMEcREDUCTASE OF FERROBACILLUS FERROOXIDANS

Abstract

The mechanism of Fe++-cytochrome c reductase was investigated. Kinetic studies on initial velocity and product inhibition, as well as spectrofluorometric studies, were consistent with a Ping Pong Bi Bi mechanism with 2 stable forms of enzyme. The Km values for the substrates were found to be 0.59 m[image] for Fe++ and 0.085 m[image] for cytochrome c. The inhibition constants for Fe+++ and reduced cytochrome c were 0.137 m[image] and 0.0135 m[image], respectively. The oxidation-reduction of non-heme iron bound to the enzyme protein was implicated as the responsible factor for the oscillation of the enzyme between its 2 forms. Nacl was a dead-end inhibitor binding the ferrous form of the enzyme, showing an un-competitive inhibition with Fe++ as a variable substrate.