ferrireduktase

Ferrireduktase, also known as ferrireductase or ferric reductase, refers to enzymes that catalyze the reduction of ferric iron (Fe3+) to ferrous iron (Fe2+). This redox reaction is a critical step in iron acquisition and mobilization in many organisms, especially when iron is scarce. Ferrireductases are typically associated with the plasma membrane or periplasm and transfer electrons from donors such as NADPH or NADH through flavin cofactors or cytochromes to external Fe3+ species, generating Fe2+ for uptake by specific transport systems.

In plants, ferrireductases are often part of the root surface ferric chelate reductase system. Members of the FRO (ferric chelate reductase) family reduce Fe3+-chelates in the rhizosphere, enabling uptake by transporters such as IRT1. Their expression is upregulated under iron deficiency and coordinated by regulatory networks including FIT. In fungi and yeasts, ferrireductases (FRE family) provide Fe2+ for import through high-affinity transporters like Ftr1; in many animals, intestinal ferrireductases such as duodenal cytochrome b (Dcytb/CYBRD1) reduce dietary Fe3+ to Fe2+ to facilitate absorption via divalent metal transporter pathways.

In bacteria and environmental contexts, ferrireductases contribute to iron cycling and respiration by reducing Fe3+ in minerals or ferric complexes, sometimes operating in conjunction with other iron-uptake or electron-transport systems. Expression and activity are commonly regulated by iron availability and environmental conditions, influencing processes from plant nutrition to microbial virulence and host–pathogen interactions.