Reaction: geranyl diphosphate + H2O = 1,8-cineole + diphosphate
For diagram of reaction click here.
Glossary: 1,8-cineole = 1,3,3-trimethyl-2-oxabicyclo[2.2.2]octane
Other name(s): 1,8-cineole cyclase; geranyl pyrophoshate:1,8-cineole cyclase; 1,8-cineole synthetase
Systematic name: geranyl-diphosphate diphosphate-lyase (cyclizing, 1,8-cineole-forming)
Comments: Requires Mn2+ or Zn2+. Mg2+ is less effective than either. 1,8-Cineol is the main product from the enzyme with just traces of other monoterpenoids. The oxygen atom is derived from water. The reaction proceeds via linalyl diphosphate and α-terpineol, the stereochemistry of both depends on the organism. However neither intermediate can substitute for geranyl diphosphate. The reaction in Salvia officinalis (sage) proceeds via (–)-(3R)-linalyl diphosphate [1-3] while that in Arabidopsis (rock cress) proceeds via (+)-(3S)-linalyl diphosphate [4].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Croteau, R., Alonso, W.R., Koepp, A.E. and Johnson, M.A. Biosynthesis of monoterpenes: partial purification, characterization, and mechanism of action of 1,8-cineole synthase. Arch. Biochem. Biophys. 309 (1994) 184-192. [PMID: 8117108]
2. Wise, M.L., Savage, T.J., Katahira, E. and Croteau, R. Monoterpene synthases from common sage (Salvia officinalis). cDNA isolation, characterization, and functional expression of (+)-sabinene synthase, 1,8-cineole synthase, and (+)-bornyl diphosphate synthase. J. Biol. Chem. 273 (1998) 14891-14899. [PMID: 9614092]
3. Peters, R.J. and Croteau, R.B. Alternative termination chemistries utilized by monoterpene cyclases: chimeric analysis of bornyl diphosphate, 1,8-cineole, and sabinene synthases. Arch. Biochem. Biophys. 417 (2003) 203-211. [PMID: 12941302]
4. Chen, F., Ro, D.K., Petri, J., Gershenzon, J., Bohlmann, J., Pichersky, E. and Tholl, D. Characterization of a root-specific Arabidopsis terpene synthase responsible for the formation of the volatile monoterpene 1,8-cineole. Plant Physiol. 135 (2004) 1956-1966. [PMID: 15299125]
5. Keszei, A., Brubaker, C.L., Carter, R., Kollner, T., Degenhardt, J. and Foley, W.J. Functional and evolutionary relationships between terpene synthases from Australian Myrtaceae. Phytochemistry 71 (2010) 844-852. [PMID: 20399476]