NAD(P) binding domain of ferredoxin reductase like phenylacetic acid (PA) degradation oxidoreductase. PA oxidoreductases of E. coli hydroxylate PA-CoA in the second step of PA degradation. Members of this group typically fuse a ferredoxin reductase-like domain with an iron-sulfur binding cluster domain. Ferredoxins catalyze electron transfer between an NAD(P)-binding domain of the alpha/beta class and a discrete (usually N-terminal) domain which vary in orientation with respect to the NAD(P) binding domain. The N-terminal portion may contain a flavin prosthetic group, as in flavoenzymes, or use flavin as a substrate. Ferredoxin-NADP+ (oxido)reductase is an FAD-containing enzyme that catalyzes the reversible electron transfer between NADP(H) and electron carrier proteins such as ferredoxin and flavodoxin. Isoforms of these flavoproteins (i.e. having a non-covalently bound FAD as a prosthetic group) are present in chloroplasts, mitochondria, and bacteria and participate in a wide variety of redox metabolic pathways. The C-terminal domain contains most of the NADP(H) binding residues and the N-terminal domain interacts non-covalently with the isoalloxazine rings of the flavin molecule which lies largely in a large gap betweed the two domains. Ferredoxin-NADP+ reductase first accepts one electron from reduced ferredoxin to form a flavin semiquinone intermediate. The enzyme then accepts a second electron to form FADH2 which then transfers two electrons and a proton to NADP+ to form NADPH.