Rubredoxin reductase

This iron-dependent enzyme [EC 1.18.1.1], also known as rubredoxin reductase, catalyzes the reaction of reduced rubredoxin and NAD+ to produce oxidized rubredoxin and NADH. 

Hydroxylases with properties similar to those of cytochrome P450 but containing nonheme iron catalyze co-oxidation of alkanes and fatty acids in certain bacteria, e.g., Pseudomonas oleovarans. A flavoprotein rubredoxin reductase, is also required.501 The methylotrophs Methylococcus and Methylosinus hydroxylate methane using as cosubstrate NADH or NADPH (Eq. 18-59). A soluble complex consists of 38-kDa reductase containing FAD and an Fe2S2... 

NADH-cytochrome f>o reductase (9) and NADPH-cytochrome P-450 reductase (10, 11) are microsomal enzymes. The latter has been referred to until very recently as NADPH-cytochrome c reductase, since that is how it is assayed, but there is no cytochrome c in microsomes and its physiological acceptor seems to be cytochrome P-460. It is thus distinguished from NADH-putidaredoxin reductase (12), NADPH-adrenodoxin reductase (13), and NADH-rubredoxin reductase (14). The adrenodoxin reductase and the rubredoxin reductase, together with their respective iron-sulfur protein acceptors, each constitute a cytochrome P-460 reductase system. 

Lee, H. J., Basran, J., and Scrutton, N. S., 1998, Electron transfer from flavin to iron in the Pseudomonas oleovorans rubredoxin reductase-rubredoxin electron transfer complex. Biochemistry 37 15513915522. 

The enzymatic system involved in hydroxylation reactions of long-chain alkanes had been previously studied by Coon and coworkers, who isolated an enzyme system from P. oleovorans that catalyzes co-hydroxylation of alkenes and fatty acids120, 106-nsl. This was resolved into three protein components rubredoxin (an iron-sulfur protein of molecular weight 19 000), an NADH-rubredoxin reductase (a flavoprotein of molecular weight 55 000) and an co-hydroxylase (characterized as being a non-heme iron protein, with one iron atom and one cysteine per polypeptide... 

Figure 1. Organization of the P. oleovorans a/fe-genes, and function of the encoded proteins. The alkane hydroxylase system consists of AlkB (alkane hydroxylase), AlkG (rubredoxin) and AlkT (rubredoxin reductase). AlkH and AlkJ are aldehyde and alcohol dehydrogenases, respectively, AlkK is an acyl-CoA synthetase, AlkL is an outer-membrane protein of unknown function, AlkF is a non-functional rubredoxin and AlkS regulates expression of the alkBFGHJKL operon.

The most intensively studied microbial epoxidizing agent is the co-hydroxylase system of Pseudomonas oleovorans [1156,1157]. It consists of three protein components rubredoxin, NADH-dependent rubredoxin reductase and an co-hydroxylase (a sensitive nonheme iron protein). It catalyzes not only the hydroxylation of aliphatic C-H bonds, but also the epoxidation of alkenes [1158, 1159]. The following rules can be formulated for epoxidations using Pseudomonas oleovorans (Scheme 2.155). 

Ueda T, Lode ET, Coon MJ. 1972. Enzymatic omega-oxidation, 6 isolation of homogeneous reduced diphosphopyridine nucleotide-rubredoxin reductase. J Biol Chem 247 2109-2116. 

NITRITE REDUCTASE NITROGENASE PYRUVATE SYNTHASE RUBREDOXIN NAD REDUCTASE STEROID 11 -HYDROXYLASE SULFITE REDUCTASE TUNGSTOENZYMES... 

R)-2-METHYLMALATE DEHYDRATASE NICOTINATE DEHYDROGENASE NITRATE REDUCTASE NITRITE REDUCTASE PHENYLALANINE MONOOXYGENASE PROLYL 3-HYDROXYLASE PROLYL 4-HYDROXYLASE PROTOCATECHUATE 3,4-DIOXYGENASE PROTOCATECHUATE 4,5-DIOXYGENASE RIESKE IRON-SULFUR PROTEIN RUBREDOXIN... 

RUBREDOXIN.NAD REDUCTASE SUCCINATE DEHYDROGENASE SULFITE REDUCTASE SULFUR DIOXYGENASE THYMIDINE 2 -HYDROXYLASE XANTHINE OXIDASE Iron(ll) hydroxide (Fe(OH)2),... 

RUBREDOXIN NAD REDUCTASE SERINE DEHYDROGENASE SORBITOL DEHYDROGENASE XANTHINE DEHYDROGENASE NAD formation,... 

A representative sampling of non-heme iron proteins is presented in Fig. 3. Evident from this atlas is the diversity of structural folds exhibited by non-heme iron proteins it may be safely concluded that there is no unique structural motif associated with non-heme iron proteins in general, or even for specific types of non-heme iron centers. Protein folds may be generally classified into several categories (i.e., all a, parallel a/)3, or antiparallel /8) on the basis of the types and interactions of secondary structures (a helix and sheet) present (Richardson, 1981). Non-heme iron proteins are found in all three classes (all a myohemerythrin, ribonucleotide reductase, and photosynthetic reaction center parallel a/)8 iron superoxide dismutase, lactoferrin, and aconitase antiparallel )3 protocatechuate dioxygenase, rubredoxins, and ferredoxins). This structural diversity is another reflection of the wide variety of functional roles exhibited by non-heme iron centers. 

Proteins with dinuclear iron centres comprise some well studied representatives like ribonucleotide reductase (RNR), purple acid phosphatase (PAP), methane monooxygenase hydroxylase (MMOH), ruberythrin and hemerythrin. The latter is an oxygen carrier in some sea worms it has been first characterized within this group and has thus laid the foundation to this class of iron coordination motif. Ruberythrin is found in anaerobic sulfate-reducing bacteria. Its name implies that, in addition to a hemerythrin-related diiron site another iron is coordinated in a mononuclear fashion relating to rubredoxin which is an iron-... 

NADH NADH-iubredoxine reductase (fp), rubredoxin (NHI) NHI Pseudomonas oleovorans fatty acid-io-hydroxylase 43-45)... 

---