The Enzyme Database

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EC 4.2.3.152     
Accepted name: 2-epi-5-epi-valiolone synthase
Reaction: α-D-sedoheptulopyranose 7-phosphate = 2-epi-5-epi-valiolone + phosphate
For diagram of valiolone biosynthesis, 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 4.2.3.155, 2-epi-valiolone synthase and EC 4.2.3.154, demethyl-4-deoxygadusol synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
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. [DOI] [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. [DOI] [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. [DOI] [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. [DOI] [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. [DOI] [PMID: 24832673]
[EC 4.2.3.152 created 2015, modified 2016]
 
 
EC 4.2.3.154     
Accepted name: demethyl-4-deoxygadusol synthase
Reaction: D-sedoheptulose 7-phosphate = demethyl-4-deoxygadusol + phosphate + H2O
For diagram of valiolone biosynthesis, click here
Glossary: demethyl-4-deoxygadusol = 2,3,5-trihydroxy-5-(hydroxymethyl)cyclohex-2-en-1-one
Other name(s): Nos2 (gene name); Anb2 (gene name)
Systematic name: D-sedoheptulose-7-phosphate phosphate-lyase (cyclizing; demethyl-4-deoxygadusol-forming)
Comments: The enzyme, characterized from the cyanobacterium Nostoc punctiforme PCC 73102, is involved in the biosynthesis of the sunscreen compound shinorine. It requires a divalent metal ion (Zn2+ or Co2+) and an NAD+ cofactor, which is transiently reduced during the reaction. cf. EC 4.2.3.152, 2-epi-5-epi-valiolone synthase and EC 4.2.3.155, 2-epi-valiolone synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Balskus, E.P. and Walsh, C.T. The genetic and molecular basis for sunscreen biosynthesis in cyanobacteria. Science 329 (2010) 1653–1656. [DOI] [PMID: 20813918]
2.  Asamizu, S., Xie, P., Brumsted, C.J., Flatt, P.M. and Mahmud, T. Evolutionary divergence of sedoheptulose 7-phosphate cyclases leads to several distinct cyclic products. J. Am. Chem. Soc. 134 (2012) 12219–12229. [DOI] [PMID: 22741921]
[EC 4.2.3.154 created 2016]
 
 
EC 4.2.3.155     
Accepted name: 2-epi-valiolone synthase
Reaction: D-sedoheptulose 7-phosphate = 2-epi-valiolone + phosphate
For diagram of valiolone biosynthesis, click here
Glossary: 2-epi-valiolone = (2S,3S,4S,5S)-2,3,4,5-tetrahydroxy-5-(hydroxymethyl)cyclohexan-1-one
Systematic name: D-sedoheptulose-7-phosphate phosphate-lyase (cyclizing; 2-epi-valiolone-forming)
Comments: The enzyme, characterized from the bacteria Actinosynnema mirum and Stigmatella aurantiaca DW4/3-1, produces 2-epi-valiolone, which is believed to function as a precursor in aminocyclitol biosynthesis. It requires a divalent metal ion (Zn2+ or Co2+) and an NAD+ cofactor, which is transiently reduced during the reaction. cf. EC 4.2.3.152, 2-epi-5-epi-valiolone synthase and EC 4.2.3.154, demethyl-4-deoxygadusol synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Asamizu, S., Xie, P., Brumsted, C.J., Flatt, P.M. and Mahmud, T. Evolutionary divergence of sedoheptulose 7-phosphate cyclases leads to several distinct cyclic products. J. Am. Chem. Soc. 134 (2012) 12219–12229. [DOI] [PMID: 22741921]
[EC 4.2.3.155 created 2016]
 
 


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