Reaction: linoleate + O2 = (8R,9Z,12Z)-8-hydroperoxyoctadeca-9,12-dienoate
Glossary: linoleate = (9Z,12Z)-octadeca-9,12-dienoate
Other name(s): linoleic acid 8R-dioxygenase; 5,8-LDS (bifunctional enzyme); 7,8-LDS (bifunctional enzyme); 5,8-linoleate diol synthase (bifunctional enzyme); 7,8-linoleate diol synthase (bifunktional enzyme); PpoA
Systematic name: linoleate:oxygen (8R)-oxidoreductase
Comments: The enzyme contains heme [1,4]. The bifunctional enzyme from Aspergillus nidulans uses different heme domains to catalyse two separate reactions. Linoleic acid is oxidized within the N-terminal heme peroxidase domain to (8R,9Z,12Z)-8-hydroperoxyoctadeca-9,12-dienoate, which is subsequently isomerized by the C-terminal P450 heme thiolate domain to (5S,8R,9Z,12Z)-5,8-dihydroxyoctadeca-9,12-dienoate (cf. EC 5.4.4.5, 9,12-octadecadienoate 8-hydroperoxide 8R-isomerase) [1]. The bifunctional enzyme from Gaeumannomyces graminis also catalyses the oxidation of linoleic acid to (8R,9Z,12Z)-8-hydroperoxyoctadeca-9,12-dienoate, but its second domain isomerizes it to (7S,8S,9Z,12Z)-5,8-dihydroxyoctadeca-9,12-dienoate (cf. EC 5.4.4.6, 9,12-octadecadienoate 8-hydroperoxide 8S-isomerase) [4].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:
References:
1. Brodhun, F., Gobel, C., Hornung, E. and Feussner, I. Identification of PpoA from Aspergillus nidulans as a fusion protein of a fatty acid heme dioxygenase/peroxidase and a cytochrome P450. J. Biol. Chem. 284 (2009) 11792-11805. [PMID: 19286665]
2. Hamberg, M., Zhang, L.-Y., Brodowsky, I.D. and Oliw, E.H. Sequential oxygenation of linoleic acid in the fungus Gaeumannomyces graminis: stereochemistry of dioxygenase and hydroperoxide isomerase reactions. Arch. Biochem. Biophys. 309 (1994) 77-80. [PMID: 8117115]
3. Garscha, U. and Oliw, E. Pichia expression and mutagenesis of 7,8-linoleate diol synthase change the dioxygenase and hydroperoxide isomerase. Biochem. Biophys. Res. Commun. 373 (2008) 579-583. [PMID: 18586008]
4. Su, C. and Oliw, E.H. Purification and characterization of linoleate 8-dioxygenase from the fungus Gaeumannomyces graminis as a novel hemoprotein. J. Biol. Chem. 271 (1996) 14112-14118. [PMID: 8662736]