IUBMB Enzyme Nomenclature


Accepted name: aflatoxin B synthase

Reaction: (1) 8-O-methylsterigmatocystin + 2 [reduced NADPH—hemoprotein reductase] + 2 O2 = aflatoxin B1 + 2 [oxidized NADPH—hemoprotein reductase] + H2O + methanol + CO2
(2) 8-O-methyldihydrosterigmatocystin + 2 [reduced NADPH—hemoprotein reductase] + 2 O2 = aflatoxin B2 + 2 [oxidized NADPH—hemoprotein reductase] + H2O + methanol + CO2

For diagram of reaction click here.

Glossary: aflatoxin B1 = (6aR,9aS)-4-methoxy-2,3,6a,9a-tetrahydrocyclopenta[c]furo[3',2':4,5]furo[2,3-h][1]benzopyran-1,11-dione
aflatoxin B2 = (6aR,9aS)-4-methoxy-2,3,6a,8,9,9a-hexahydrocyclopenta[c]furo[3',2':4,5]furo[2,3-h][1]benzopyran-1,11-dione
8-O-methylsterigmatocystin = 6,8-dimethoxy-3a,12c-dihydrofuro[3',2':4,5]furo[2,3-c]xanthen-7-one
8-O-methyldihydrosterigmatocystin = 6,8-dimethoxy-1,2,3a,12c-tetrahydrofuro[3',2':4,5]furo[2,3-c]xanthen-7-one

Other name(s): ordA (gene name)

Systematic name: 8-O-methylsterigmatocystin,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (aflatoxin-B forming)

Comments: A cytochrome P-450 (heme-thiolate) protein. Isolated from the mold Aspergillus parasiticus.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Bhatnagar, D., Cleveland, T.E. and Kingston, D.G. Enzymological evidence for separate pathways for aflatoxin B1 and B2 biosynthesis. Biochemistry 30 (1991) 4343-4350. [PMID: 1902378]

2. Yu, J., Chang, P.K., Ehrlich, K.C., Cary, J.W., Montalbano, B., Dyer, J.M., Bhatnagar, D. and Cleveland, T.E. Characterization of the critical amino acids of an Aspergillus parasiticus cytochrome P-450 monooxygenase encoded by ordA that is involved in the biosynthesis of aflatoxins B1, G1, B2, and G2. Appl. Environ. Microbiol. 64 (1998) 4834-4841. [PMID: 9835571]

3. Udwary, D.W., Casillas, L. K. and Townsend, C.A. Synthesis of 11-hydroxyl O-methylsterigmatocystin and the role of a cytochrome P-450 in the final step of aflatoxin biosynthesis. J. Am. Chem. Soc. 124 (2002) 5294-5303. [PMID: 11996570]

[EC created 2013 as EC, transferred 2018 to EC]

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