EC 1.14.15.37     
Accepted name: luteothin monooxygenase
Reaction: luteothin + 2 O2 + 4 reduced ferredoxin [iron-sulfur] cluster + 4 H+ = aureothin + 3 H2O + 4 oxidized ferredoxin [iron-sulfur] cluster (overall reaction)
(1a) luteothin + O2 + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ = (7R)-7-hydroxyluteothin + H2O + 2 oxidized ferredoxin [iron-sulfur] cluster
(1b) (7R)-7-hydroxyluteothin + O2 + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ = aureothin + 2 H2O + 2 oxidized ferredoxin [iron-sulfur] cluster
Glossary: luteothin = 2-[(3E,5E)-3,5-dimethyl-6-(4-nitrophenyl)hexa-3,5-dien-1-yl]-6-methoxy-3,5-dimethyl-4H-pyran-4-one
aureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E)-2-methyl-3-(4-nitrophenyl)prop-2-en-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
spectinabilin = neoaureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E,4E,6E)-2,4,6-trimethyl-7-(4-nitrophenyl)hepta-2,4,6-trien-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
Other name(s): aurH (gene name)
Systematic name: luteothin,ferredoxin:oxygen oxidoreductase (aureothin-forming)
Comments: The enzyme, characterized from the bacterium Streptomyces thioluteus, is a bifunctional cytochrome P-450 (heme-thiolate) protein that catalyses both the hydroxylation of its substrate and formation of a furan ring, the final step in the biosynthesis of the antibiotic aureothin. In the bacteria Streptomyces orinoci and Streptomyces spectabilis an orthologous enzyme catalyses a similar reaction that forms spectinabilin.
References:
1.  He, J., Muller, M. and Hertweck, C. Formation of the aureothin tetrahydrofuran ring by a bifunctional cytochrome P450 monooxygenase. J. Am. Chem. Soc. 126 (2004) 16742–16743. [PMID: 15612710]
2.  Traitcheva, N., Jenke-Kodama, H., He, J., Dittmann, E. and Hertweck, C. Non-colinear polyketide biosynthesis in the aureothin and neoaureothin pathways: an evolutionary perspective. ChemBioChem 8 (2007) 1841–1849. [PMID: 17763486]
[EC 1.14.15.37 created 2019]
 
 
EC 1.14.99.68     
Accepted name: 4-aminobenzoate N-oxygenase
Reaction: 4-aminobenzoate + reduced acceptor + 2 O2 = 4-nitrobenzoate + acceptor + 2 H2O
Glossary: aureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E)-2-methyl-3-(4-nitrophenyl)prop-2-en-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
Other name(s): aurF (gene name)
Systematic name: 4-aminobenzoate,acceptor:oxygen oxidoreductase (N-hydroxylating)
Comments: The enzyme, characterized from the bacterium Streptomyces thioluteus, catalyses an early step in the biosynthesis of the antibiotic aureothin. It contains a carboxylate-bridged binuclear non-heme iron cluster. The native electron donor has not been identified, but is likely an iron-sulfur protein. The reaction mechanism involves formation of an extremely stable peroxo intermediate that catalyses three two-electron oxidations via a hydroxylamine and dihydroxylamine intermediates. cf. EC 1.14.99.67, N-[1-(4-aminophenyl)-1,3-dihydroxypropan-2-yl]-2,2-dichloroacetamide N-oxygenase.
References:
1.  He, J. and Hertweck, C. Biosynthetic origin of the rare nitroaryl moiety of the polyketide antibiotic aureothin: involvement of an unprecedented N-oxygenase. J. Am. Chem. Soc. 126 (2004) 3694–3695. [PMID: 15038705]
2.  Lee, J. and Zhao, H. Mechanistic studies on the conversion of arylamines into arylnitro compounds by aminopyrrolnitrin oxygenase: identification of intermediates and kinetic studies. Angew. Chem. Int. Ed. Engl. 45 (2006) 622–625. [PMID: 16342311]
3.  Zocher, G., Winkler, R., Hertweck, C. and Schulz, G.E. Structure and action of the N-oxygenase AurF from Streptomyces thioluteus. J. Mol. Biol. 373 (2007) 65–74. [PMID: 17765264]
4.  Choi, Y.S., Zhang, H., Brunzelle, J.S., Nair, S.K. and Zhao, H. In vitro reconstitution and crystal structure of p-aminobenzoate N-oxygenase (AurF) involved in aureothin biosynthesis. Proc. Natl. Acad. Sci. USA 105 (2008) 6858–6863. [PMID: 18458342]
5.  Korboukh, V.K., Li, N., Barr, E.W., Bollinger, J.M., Jr. and Krebs, C. A long-lived, substrate-hydroxylating peroxodiiron(III/III) intermediate in the amine oxygenase, AurF, from Streptomyces thioluteus. J. Am. Chem. Soc. 131 (2009) 13608–13609. [PMID: 19731912]
6.  Li, N., Korboukh, V.K., Krebs, C. and Bollinger, J.M., Jr. Four-electron oxidation of p-hydroxylaminobenzoate to p-nitrobenzoate by a peroxodiferric complex in AurF from Streptomyces thioluteus. Proc. Natl. Acad. Sci. USA 107 (2010) 15722–15727. [PMID: 20798054]
[EC 1.14.99.68 created 2020]
 
 
EC 2.1.1.353     
Accepted name: demethylluteothin O-methyltransferase
Reaction: S-adenosyl-L-methionine + demethylluteothin = S-adenosyl-L-homocysteine + luteothin
Glossary: luteothin = 2-[(3E,5E)-3,5-dimethyl-6-(4-nitrophenyl)hexa-3,5-dien-1-yl]-6-methoxy-3,5-dimethyl-4H-pyran-4-one
aureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E)-2-methyl-3-(4-nitrophenyl)prop-2-en-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
spectinabilin = neoaureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E,4E,6E)-2,4,6-trimethyl-7-(4-nitrophenyl)hepta-2,4,6-trien-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
Other name(s): aurI (gene name)
Systematic name: S-adenosyl-L-methionine:demethylluteothin O-methyltransferase
Comments: The enzyme, characterized from the bacterium Streptomyces thioluteus, participates in the biosynthesis of the antibiotic aureothin. An orthologous enzyme in the bacteria Streptomyces orinoci and Streptomyces spectabilis catalyses a similar reaction in the biosynthesis of spectinabilin.
References:
1.  He, J., Muller, M. and Hertweck, C. Formation of the aureothin tetrahydrofuran ring by a bifunctional cytochrome P450 monooxygenase. J. Am. Chem. Soc. 126 (2004) 16742–16743. [PMID: 15612710]
2.  Muller, M., He, J. and Hertweck, C. Dissection of the late steps in aureothin biosynthesis. ChemBioChem 7 (2006) 37–39. [PMID: 16292785]
[EC 2.1.1.353 created 2019]
 
 
EC 2.3.1.289     
Accepted name: aureothin polyketide synthase system
Reaction: 4-nitrobenzoyl-CoA + malonyl-CoA + 4 (S)-methylmalonyl-CoA + 4 NADPH + 4 H+ = demethylluteothin + 5 CO2 + 6 CoA + 4 NADP+ + 3 H2O
Glossary: demethylluteothin = nordeoxyaureothin = 2-[(3E,5E)-3,5-dimethyl-6-(4-nitrophenyl)hexa-3,5-dien-1-yl]-6-hydroxy-3,5-dimethyl-4H-pyran-4-one
aureothin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E)-2-methyl-3-(4-nitrophenyl)prop-2-en-1-ylidene]oxolan-2-yl]-4H-pyran-4-one
Other name(s): aurABC (gene names); aureothin polyketide synthase complex
Systematic name: malonyl-CoA/(S)-methylmalonyl-CoA:4-nitrobenzoyl-CoA (methyl)malonyltransferase (demethylluteothin-forming)
Comments: This polyketide synthase, characterized from the bacterium Streptomyces thioluteus, generates the backbone of the antibiotic aureothin. It is composed of 4 modules that total 18 domains and is encoded by three genes. The enzyme accepts the unusual starter unit 4-nitrobenzoyl-CoA and extends it by 4 molecules of (S)-methylmalonyl-CoA and a single molecule of malonyl-CoA. The first module (encoded by aurA) is used twice in an iterative fashion, so that the five Claisen condensation reactions are catalysed by only four modules. The iteration becomes possible by the transfer of the [acp]-bound polyketide intermediate back to the ketosynthase (KS) domain on the opposite polyketide synthase strand (polyketides are homodimeric).
References:
1.  He, J. and Hertweck, C. Iteration as programmed event during polyketide assembly; molecular analysis of the aureothin biosynthesis gene cluster. Chem. Biol. 10 (2003) 1225–1232. [PMID: 14700630]
2.  He, J. and Hertweck, C. Functional analysis of the aureothin iterative type I polyketide synthase. ChemBioChem 6 (2005) 908–912. [PMID: 15812854]
3.  Busch, B., Ueberschaar, N., Sugimoto, Y. and Hertweck, C. Interchenar retrotransfer of aureothin intermediates in an iterative polyketide synthase module. J. Am. Chem. Soc. 134 (2012) 12382–12385. [PMID: 22799266]
[EC 2.3.1.289 created 2019]
 
 
EC 2.3.1.290     
Accepted name: spectinabilin polyketide synthase system
Reaction: 4-nitrobenzoyl-CoA + malonyl-CoA + 6 (S)-methylmalonyl-CoA + 6 NADPH + 4 H+ = demethyldeoxyspectinabilin + 7 CO2 + 8 CoA + 6 NADP+ + 5 H2O
Glossary: demethyldeoxyspectinabilin = 2-hydroxy-3,5-dimethyl-6-[(3E,5E,7E,9E)-3,5,7,9-tetramethyl-10-(4-nitrophenyl)deca-3,5,7,9-tetraen-1-yl]pyran-4-one
spectinabilin = 2-methoxy-3,5-dimethyl-6-[(2R,4Z)-4-[(2E,4E,6E)-2,4,6-trimethyl-7-(4-nitrophenyl)hepta-2,4,6-trien-1-ylidene]oxolan-2-yl]pyran-4-one
Other name(s): norAA’BC (gene names); spectinabilin polyketide synthase complex
Systematic name: malonyl-CoA/(S)-methylmalonyl-CoA:4-nitrobenzoyl-CoA (methyl)malonyltransferase (demethyldeoxyspectinabilin-forming)
Comments: This polyketide synthase, characterized from the bacteria Streptomyces orinoci and Streptomyces spectabilis, generates the backbone of the antibiotic spectinabilin. It is composed of 6 modules that total 28 domains and is encoded by four genes. The enzyme accepts the unusual starter unit 4-nitrobenzoyl-CoA and extends it by 6 molecules of (S)-methylmalonyl-CoA and a single molecule of malonyl-CoA. The first module (encoded by norA) is used twice in an iterative fashion, so that the seven Claisen condensation reactions are catalysed by only six modules. The iteration becomes possible by the transfer of the [acp]-bound polyketide intermediate back to the ketosynthase (KS) domain on the opposite polyketide synthase strand (polyketides are homodimeric).
References:
1.  Traitcheva, N., Jenke-Kodama, H., He, J., Dittmann, E. and Hertweck, C. Non-colinear polyketide biosynthesis in the aureothin and neoaureothin pathways: an evolutionary perspective. ChemBioChem 8 (2007) 1841–1849. [PMID: 17763486]
2.  Choi, Y.S., Johannes, T.W., Simurdiak, M., Shao, Z., Lu, H. and Zhao, H. Cloning and heterologous expression of the spectinabilin biosynthetic gene cluster from Streptomyces spectabilis. Mol. Biosyst. 6 (2010) 336–338. [PMID: 20094652]
[EC 2.3.1.290 created 2019]