The Enzyme Database

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EC 4.2.1.123     
Accepted name: tetrahymanol synthase
Reaction: tetrahymanol = squalene + H2O
For diagram of hopene biosynthesis, click here
Glossary: tetrahymanol = gammaceran-3β-ol
Other name(s): squalene—tetrahymanol cyclase
Systematic name: squalene hydro-lyase (tetrahymanol forming)
Comments: The reaction occurs in the reverse direction.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Saar, J., Kader, J.C., Poralla, K. and Ourisson, G. Purification and some properties of the squalene-tetrahymanol cyclase from Tetrahymena thermophila. Biochim. Biophys. Acta 1075 (1991) 93–101. [DOI] [PMID: 1892870]
2.  Giner, J.L., Rocchetti, S., Neunlist, S., Rohmer, M. and Arigoni, D. Detection of 1,2-hydride shifts in the formation of euph-7-ene by the squalene-tetrahymanol cyclase of Tetrahymena pyriformis. Chem. Commun. (Camb.) (2005) 3089–3091. [DOI] [PMID: 15959594]
[EC 4.2.1.123 created 2011]
 
 
EC 4.2.1.129     
Accepted name: squalene—hopanol cyclase
Reaction: hopan-22-ol = squalene + H2O
For diagram of hopene and tetrahymanol biosynthesis, click here
Other name(s): squalene—hopene cyclase (ambiguous)
Systematic name: hopan-22-ol hydro-lyase
Comments: The enzyme produces the cyclization products hopene (cf. EC 5.4.99.17) and hopanol from squalene at a constant ratio of 5:1.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Hoshino, T., Nakano, S., Kondo, T., Sato, T. and Miyoshi, A. Squalene-hopene cyclase: final deprotonation reaction, conformational analysis for the cyclization of (3R,S)-2,3-oxidosqualene and further evidence for the requirement of an isopropylidene moiety both for initiation of the polycyclization cascade and for the formation of the 5-membered E-ring. Org Biomol Chem 2 (2004) 1456–1470. [DOI] [PMID: 15136801]
2.  Sato, T., Kouda, M. and Hoshino, T. Site-directed mutagenesis experiments on the putative deprotonation site of squalene-hopene cyclase from Alicyclobacillus acidocaldarius. Biosci. Biotechnol. Biochem. 68 (2004) 728–738. [PMID: 15056909]
[EC 4.2.1.129 created 2011]
 
 


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