The Interaction of Ferredoxin with Ferredoxin-Dependent Enzymes

Abstract

Ferredoxin, reduced by Photosystem I (PS I) in the light, serves as the electron donor for the reduction of NADP + to NADPH, of sulfite to sulfide, of nitrite to ammonia and for the reductant-requiring of glutamate and 2-oxoglutarate to glutamate in all oxygenic photosynthetic organisms. Reduced ferredoxin also serves as the electron donor for the reduction of nitrate to nitrite in cyanobacteria. In addition to its role in supplying a source of electrons for the net reduction of oxidized species in reductant-requiring assimilatory pathways, reduced ferredoxin plays an important role, via the ferredoxin/thioredoxin system, in the regulation of carbon assimilation and other pathways. This chapter focuses on the interactions between ferredoxin and six enzymes that utilize reduced ferredoxin as an electron donor (NADP + reductase, nitrate reductase, nitrite reductase, glutamate synthase, sulfite reductase, and thioredoxin reductase). The mechanisms of several of these enzymes will also be discussed.