Reaction: α-D-sedoheptulopyranose 7-phosphate = 2-epi-5-epi-valiolone + phosphate
For diagram of reaction click here.
Glossary: 2-epi-5-epi-valiolone = (2S,3S,4S,5R)-2,3,4,5-tetrahydroxy-5-(hydroxymethyl)cyclohexan-1-one
Other name(s): AcbC; ValA; CetA; SalQ; C7-cyclitol synthase
Systematic name: α-D-sedoheptulopyranose-7-phosphate phosphate-lyase (cyclizing; 2-epi-5-epi-valiolone-forming)
Comments: The enzyme is highly specific for α-D-sedoheptulopyranose 7-phosphate. It requires a divalent metal ion (Zn2+ or Co2+) and an NAD+ cofactor, which is transiently reduced during the reaction.The enzyme is involved in the biosynthesis of C7N-aminocyclitol natural products, such as the valienamine moiety of the antidiabetic drug acarbose and the crop protectant validamycin A. cf. EC 126.96.36.199, 2-epi-valiolone synthase and EC 188.8.131.52, desmethyl-4-deoxygadusol synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Stratmann, A., Mahmud, T., Lee, S., Distler, J., Floss, H.G. and Piepersberg, W. The AcbC protein from Actinoplanes species is a C7-cyclitol synthase related to 3-dehydroquinate synthases and is involved in the biosynthesis of the α-glucosidase inhibitor acarbose. J. Biol. Chem. 274 (1999) 10889-10896. [PMID: 10196166]
2. Yu, Y., Bai, L., Minagawa, K., Jian, X., Li, L., Li, J., Chen, S., Cao, E., Mahmud, T., Floss, H.G., Zhou, X. and Deng, Z. Gene cluster responsible for validamycin biosynthesis in Streptomyces hygroscopicus subsp. jinggangensis 5008. Appl. Environ. Microbiol. 71 (2005) 5066-5076. [PMID: 16151088]
3. Wu, X., Flatt, P.M., Schlorke, O., Zeeck, A., Dairi, T. and Mahmud, T. A comparative analysis of the sugar phosphate cyclase superfamily involved in primary and secondary metabolism. Chembiochem 8 (2007) 239-248. [PMID: 17195255]
4. Choi, W.S., Wu, X., Choeng, Y.H., Mahmud, T., Jeong, B.C., Lee, S.H., Chang, Y.K., Kim, C.J. and Hong, S.K. Genetic organization of the putative salbostatin biosynthetic gene cluster including the 2-epi-5-epi-valiolone synthase gene in Streptomyces albus ATCC 21838. Appl. Microbiol. Biotechnol. 80 (2008) 637-645. [PMID: 18648803]
5. Kean, K.M., Codding, S.J., Asamizu, S., Mahmud, T. and Karplus, P.A. Structure of a sedoheptulose 7-phosphate cyclase: ValA from Streptomyces hygroscopicus. Biochemistry 53 (2014) 4250-4260. [PMID: 24832673]