| Type: | Domain | Name: | Pyridine nucleotide-disulphide oxidoreductase, FAD/NAD(P)-binding domain |
| Description: | FAD flavoproteins belonging to the family of pyridine nucleotide-disulphide oxidoreductases (glutathione reductase, trypanothione reductase, lipoamide dehydrogenase, mercuric reductase, thioredoxin reductase, alkyl hydroperoxide reductase) share sequence similarity with a number of other flavoprotein oxidoreductases, in particular with ferredoxin-NAD+ reductases involved in oxidative metabolism of a variety of hydrocarbons (rubredoxin reductase, putidaredoxin reductase, terpredoxin reductase, ferredoxin-NAD+ reductase components of benzene 1,2-dioxygenase, toluene 1,2-dioxygenase, chlorobenzene dioxygenase, biphenyl dioxygenase), NADH oxidase and NADH peroxidase [, , ]. Comparison of the crystal structures of human glutathione reductase and Escherichia colithioredoxin reductase reveals different locations of their active sites, suggesting that the enzymes diverged from an ancestral FAD/NAD(P)H reductase and acquired their disulphide reductase activities independently []. Despite functional similarities, oxidoreductases of this family show no sequence similarity with adrenodoxin reductases [] and flavoprotein pyridine nucleotidecytochrome reductases (FPNCR) []. Assuming that disulphide reductase activity emerged later, during divergent evolution, the family can be referred to as FAD-dependent pyridine nucleotide reductases, FADPNR.To date, 3D structures of glutathione reductase [], thioredoxin reductase [], mercuric reductase [], lipoamide dehydrogenase [], trypanothione reductase [] and NADH peroxidase [] have been solved. The enzymes share similar tertiary structures based on a doubly-wound alpha/beta fold, but the relative orientations of their FAD- and NAD(P)H-binding domains may vary significantly. By contrast with the FPNCR family, the folds of the FAD- and NAD(P)H-binding domains are similar, suggesting that the domains evolved by gene duplication [].This entry describes the FAD binding domain which has a nested NADH binding domain and is found in both class I and class II oxidoreductases. | Short Name: | Pyr_nucl-diS_OxRdtase_FAD/NAD |
