The Plant–Type Ferredoxin-NADP+ Reductases

Abstract

This group can be further classified into a plastidic and a bacterial class, which differ not only in their sequences, but also in the environment of the active site, FAD conformations and catalytic efficiencies (Carrillo & Ceccarelli, 2003). Plastidic FNRs display high catalytic efficiencies (turnover numbers in the range 100-600 s-1), whereas bacterial reductases are much less active (Ceccarelli et al., 2004). In plants and cyanobacteria, optimization for FNR catalytic efficiency might be related to the demands of the photosynthetic process that requires a very fast electron flow to sustain CO 2 fixation rates. In organisms growing on heterotrophic metabolisms or anoxygenic photosynthesis, FNR is involved in pathways that proceed at a much lower pace, acting as a shuttle between the abundant NAD(P)H pool and the low potential electron carriers. This chapter will focus on structural and functional aspects of the ferredoxin-NADP(H) reductase in association with the metabolic process of photosynthesis. Special attention will be pay to techniques and approaches that could help to appreciate the importance of the enzyme and to understand, conceive and/or execute research on FNR.