Reaction: tetracenomycin A2 + 2 O2 + 2 NAD(P)H + 2 H+ = tetracenomycin C + 2 NAD(P)+ + H2O
For diagram of reaction click here and for mechanism click here.
Glossary: tetracenomycin A2 = methyl 10,12-dihydroxy-3,8-dimethoxy-1-methyl-6,11-dioxo-6,11-dihydrotetracene-2-carboxylate
tetracenomycin C = methyl (6aR,7S,10aR)-6a,7,10a,12-tetrahydroxy-3,8-dimethoxy-1-methyl-6,10,11-trioxo-6,6a,7,10,10a,11-hexahydrotetracene-2-carboxylate
Other name(s): TcmG; ElmG; tetracenomycin A2,NAD(P)H:O2 oxidoreductase (tetracenomycin C forming)
Systematic name: tetracenomycin A2,NAD(P)H:oxygen oxidoreductase (tetracenomycin C forming)
Comments: Isolated from the bacterium Streptomyces glaucescens. The enzyme was also isolated from the bacterium Streptomyces olivaceus, where it acts on 8-demethyltetracenomycin A2 (tetracenomycin B2) as part of elloramycin biosynthesis. The reaction involves a monooxygenase reaction which is followed by a dioxygenase reaction giving a gem-diol and an epoxide. Water opens the epoxide giving two hydroxy groups. The gem-diol eliminates water to give a ketone which is then reduced to a hydroxy group.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:
References:
1. Shen, B. and Hutchinson, C.R. Triple hydroxylation of tetracenomycin A2 to tetracenomycin C in Streptomyces glaucescens. Overexpression of the tcmG gene in Streptomyces lividans and characterization of the tetracenomycin A2 oxygenase. J. Biol. Chem. 269 (1994) 30726-30733. [PMID: 7982994]
2. Rafanan, E.R., Jr., Hutchinson, C.R. and Shen, B. Triple hydroxylation of tetracenomycin A2 to tetracenomycin C involving two molecules of O2 and one molecule of H2O. Org. Lett. 2 (2000) 3225-3227. [PMID: 11009387]
3. Beynon, J., Rafanan, E.R., Jr., Shen, B. and Fisher, A.J. Crystallization and preliminary X-ray analysis of tetracenomycin A2 oxygenase: a flavoprotein hydroxylase involved in polyketide biosynthesis. Acta Crystallogr. D Biol. Crystallogr. 56 (2000) 1647-1651. [PMID: 11092935]