EXTRACELLULAR IRON REDUCTASE-ACTIVITY PRODUCED BY LISTERIA-MONOCYTOGENES

Little is known about how pathogenic microorganisms that do not produc e low-molecular-weight iron-chelating agents, termed siderophores, acq uire iron from their environment. We have identified an extracellular enzyme produced by Listeria monocytogenes that can mobilize iron from a variety of iron-chelate complexes via reduction of the metal. The ir on reductase requires Mg2+, flavin mononucleotide (FMN), and reduced n icotinamide adenine dinucleotide (NADH) for activity. Saturation kinet ics were found when initial velocity studies of iron reduction were ca rried out as a function of variable FMN concentrations in the presence of 100 mu M NADH and 10 mM Mg2+. Hyperbolic kinetics were also found when these studies were repeated as a function of variable NADH concen trations along with 20 mu M FMN and 10 mM Mg2+. This process of extrac ellular reduction, in all likelihood, could be involved in the mobiliz ation of iron from soils and aqueous environments and from host tissue s in pathogenic processes, This is the first report of the extracellul ar enzymic reduction of iron by microorganisms.