NADP reductase

The immediate electron acceptor for P700 is a special molecule of chlorophyll. This unique Chi a (Aq) rapidly passes the electron to a specialized quinone (Aj), which in turn passes the e to the first in a series of membrane-bound ferredoxins (Fd, Chapter 21). This Fd series ends with a soluble form of ferredoxin, Fd, which serves as the immediate electron donor to the fiavo-protein (Fp) that catalyzes NADP reduction, namely, ferredoxin NADP reductase. 

The third study has employed 4,6-dinitrobenzofuroxan and as metabolic systems the one-electron reductants NADPHxytochrome P450 reductase and ferredoxin NADP(+) reductase and the two-electron reductants DT-diaphorase and Enterobacter cloacae nitroreductase [239]. The compound is activated either by DT-diaphorase or nitroreductase. 

Fig. 16. Ferredoxin (Fd)/ferredoxin-NADP+-reductase (FNR) mediated enzymatic carboxylation of pyruvic acid to form malic acid catalyzed by the NADPH-dependent malic enzyme (ME)...

DIHYDROOROTATE OXIDASE DIMETHYLANILINE MONOOXYCENASE FERREDOXIN NADP REDUCTASE GLUTATHIONE REDUCTASE 0-2-HYDROXY ACID DEHYDROGENASE... 

RESONANCE RAMAN SPECTROSCOPY Ferredoxin-dependent enzymes, ADRENODOXIN BENZENE 1,2-DIOXYGENASE FERREDOXIN NADP REDUCTASE GLUTAMATE SYNTHASE HYDROGENASE... 

Pyridine nucleotide-dependent flavoenzyme catalyzed reactions are known for the external monooxygenase and the disulfide oxidoreductases However, no evidence for the direct participation of the flavin semiquinone as an intermediate in catalysis has been found in these systems. In contrast, flavin semiquinones are necessary intermediates in those pyridine nucleotide-dependent enzymes in which electron transfer from the flavin involves an obligate 1-electron acceptor such as a heme or an iron-sulfur center. Examples of such enzymes include NADPH-cytochrome P4S0 reductase, NADH-cytochrome bs reductase, ferredoxin — NADP reductase, adrenodoxin reductase as well as more complex enzymes such as the mitochondrial NADH dehydrogenase and xanthine dehydrogenase. 

The catalytic significance of this observation is not known since no deviation from a two-electron Nemst plot is observed with NADH as reductant and no kinetic studies have been done to compare the rate of the NAD -facilitated comproportionation reaction with the rate of catalytic turnover. No comparable studies on the effect of NADP on the oxidation-reduction potential of ferredoxin-NADP reductase have been, to our knowledge, published. Inasmuch as the physiological role for this enzyme is reduction of the pyridine nucleotide rather than its oxidation, the potential of the enzyme should be significantly lower than that of the pyridine nucleotide couple. Indeed, a value of —445 mV has been determined for this flavoenzyme with the driving force for its reduction being due to a decrease of 90 mV in the one-electron potential of the ferredoxin reductant. This increase... 

The primary structures of at least 28 [2Fe-2S] proteins have been determined.737 Twenty-six of these have been isolated from plants or algae. The remaining two are from halobacteria, and have about 20 extra residues at the N-terminus and about five extra residues at the C-terminus in comparison with the plant-type proteins. These structural differences will account for their physiological differences. Thus, the halobacteria] ferredoxin does not form a complex with ferredoxin-NADP reductase, in contrast with plant-type [2Fe-2S] ferredoxins. 

Michalowski, C.B., Schmitt, J.M. Bohnert, H.J. (1989ft). Expression during salt stress and nucleotide sequence of cDNA for ferredoxin-NADP+ reductase from M. crystallinum. Plant Physiology 89,817-23. 

Ferridoxine NADP reductase Wheat Increase of activity Riov Brown, 1976... 

Riov, J. Brown, G.N. (1976). Comparative studies of activity and properties of ferrodoxin-NADP+ reductase during cold hardening of wheat. Candian Journal of Botany 54, 1896-902. 

FIGURE 21. Photosystem I (PS I). P700, special pair Q, plastoquinone QH2, dihy-droplastoquinone NADP, nicotinamide adenine dinucleotide phosphate FQR, ferre-doxin-quinone reductase FNR, ferredoxin-NADP reductase Fd, ferredoxin ADP, adenosine diphosphate ATP, adenosine triphosphate. 

S Nakamura. Initiation of sulfite oxidation by spinach ferredoxin-NADP reductase and ferredoxin system a model experiment of the superoxide anion radical production by metalloflavoproteins. Biochem Biophys Res Commun 41 177-183, 1970. 

Two high-energy electrons from two molecules of reduced ferredoxin are now transferred to NADP+ to form NADPH. The reaction is carried out by NADP reductase. 

Scheme 4.104 PikC-catalyzed hydroxylation ofYC-17 to methymycin and neomethymycin in the presence of NADPH, ferredoxin and ferredoxin-NADP+ reductase [433].

Fig. 6. Sites of inhibitory action of DCMU in photosynthetic electron transport chain. The abbreviations are as follows - Cyt f cytochrome f, Fd ferredoxin, Mn water-splitting complex (manganese-containing), P680 pigment complex of photosystem II, P700 pigment complex of photosystem I, PC plastocyanin, PQ plastquinone, Q quencher, Rd NADP reductase and X direct electron acceptor complex...

Vollmer M, Thomsen N, Wiek S, Seeber F (2001) Apicomplexan parasites possess distinct nuclear-encoded, but apicoplast-localized, plant-type ferredoxin-NADP(+) reductase and ferredoxin. J Biol Chem 276 5483-5490... 

Yamanaka, T. and M. D. Kamen Purification of an NADP-reductase and of ferredoxin derived from the facultative photoheterotroph, Rhodopseudomonas palustris. Biochem. Biophys. Res. Commun. 18, 611—616 (1965). 

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