NADPH-oxido-reductase

In-vitro approach Data are available in abundance concerning metal effects on isolated chloroplasts (for a review, see Clijsters and Van Assche, 1985). All the metals studied were found to be potential inhibitors of photosystem 2 (PS 2) photosystem 1 (PS 1) was reported to be less sensitive. From the in-vitro experiments, at least two potential metal-sensitive sites can be derived in the photosynthetic electron transport chain the water-splitting enzyme at the oxidising side of PS 2, and the NADPH-oxido-reductase (an enzyme with functional SH-groups) at the reducing side of PS 1 (Clijsters and Van Assche, 1985). Moreover, in vitro, non cyclic photophosphorylation was very sensitive to lead (Hampp et al., 1973 b) and mercury (Honeycutt and Korgmann, 1972). Both cyclic and non-cyclic photophosphorylation were proven to be inhibited by excess of copper (Uribe and Stark, 1982) and cadmium (Lucero et al, 1976). 

L-Phenylalanine,which is derived via the shikimic acid pathway,is an important precursor for aromatic aroma components. This amino acid can be transformed into phe-nylpyruvate by transamination and by subsequent decarboxylation to 2-phenylacetyl-CoA in an analogous reaction as discussed for leucine and valine. 2-Phenylacetyl-CoA is converted into esters of a variety of alcohols or reduced to 2-phenylethanol and transformed into 2-phenyl-ethyl esters. The end products of phenylalanine catabolism are fumaric acid and acetoacetate which are further metabolized by the TCA-cycle. Phenylalanine ammonia lyase converts the amino acid into cinnamic acid, the key intermediate of phenylpropanoid metabolism. By a series of enzymes (cinnamate-4-hydroxylase, p-coumarate 3-hydroxylase, catechol O-methyltransferase and ferulate 5-hydroxylase) cinnamic acid is transformed into p-couma-ric-, caffeic-, ferulic-, 5-hydroxyferulic- and sinapic acids,which act as precursors for flavor components and are important intermediates in the biosynthesis of fla-vonoides, lignins, etc. Reduction of cinnamic acids to aldehydes and alcohols by cinnamoyl-CoA NADPH-oxido-reductase and cinnamoyl-alcohol-dehydrogenase form important flavor compounds such as cinnamic aldehyde, cin-namyl alcohol and esters. Further reduction of cinnamyl alcohols lead to propenyl- and allylphenols such as... 

Neutrophils and macrophages perform the same enzymatic function with a NADPH oxidoreductase (109). The superoxide produced by this NADPH oxido-reductase reduces the metal complexed to silica and asbestos, dislodging it from the dust (26) ... 

NADPH quinone oxido-reductase 1 Pro187Ser variant occurring with about 5% frequency is functionally almost completely deficient. Impaired activity associated with benzene toxicity and cancer chemotherapy induced leukemia. 

At the time PS 11 absorbs a photon, PS-1 complex also absorbs a photon, resulting in a charge separation to form the oxidized primary electron donor P700 and the reduced primary electron acceptor Aq. The oxidized primary donor P700 is then reduced by an electron from reduced plastocyanin. The electron on the primary acceptor Aq is rapidly transferred step-wise through a series of acceptors consisting of a phylloquinone (0 Q), three iron-sulfur clusters in FeS-X, FeS-A and FeS-B, and finally ferredoxin (Fd) which reduces NADP" to NADPH in a reaction catalyzed by NADP -ferredoxin reductase (FNR). The PS-1 complex is also called the plastocyanin-ferredoxin oxido-reductase. ... 

Conveniently, both NADPH cytochrome P450 oxido-reductase (POR) and cytochrome b5 are also anchored... 

Preparation of various (iS)-3-hydroxy-carboxylates by reducing 130 mM solutions of tbe corresponding 3-oxo carboxylates with purified (5)-3-bydroxy carboxylate oxido-reductase from C. tyrobutyricum (109) and tbe regeneration of NADPH (83). 

Systematic name of the enzyme 10-deoxysarpagine, NADPH oxygen oxido-reductase. 

Thioredoxin (1,2) are small (M. 11-12,000) ubiquitous redox proteins with two half-cystine residues in the conserved active site structure Trp-Cys-Gly-Pro-Cys. The oxidized form Trx-S2 is reduced by NADPH and thioredoxin-reductase the reduced rorm Trx(SH)2 is a powerful protein disulfide oxido-reductase which regulatesthe activity of enzymes by thiol redox control it serves as hydrogen donor for various reductive enzymes such as ribonucleotide reductase or enzymes reducing sulfate or methionine sulfoxide. Also, Trx(SH)2 is essential for phage T7 DNA replication as a subunit of T7 DNA polymerase and assembly of filamentous phages (fl and M13), at least in E, ooti. 

Working together, photosystem I and the enzyme ferredoxin NADP oxido-reductase catalyze the hght-induced reduction of NADP to NADPH. The electrons required for this process come initially from P700 in its excited state. The resulting P700 is then reduced by the mobile carrier plastocyanin (Pc), a protein in which the boimd copper ion can exist in oxidation states +2 and +1. The net reaction is... 

Schauer, R., 1970c, Biosynthesis of A-glycoloylneuraminic acid by an ascorbate or NADPH-dependent, N-acetyl hydroxylating W-acetylneuraminate oxygen oxido-reductase in homogenates of porcine submaxillary gland, Z. Physiol. Chem. 351 783. 

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