Reaction: (1E,4S,5E,7R)-germacra-1(10),5-dien-11-ol + H2O = (–)-geosmin + acetone
For diagram of reaction click here and mechanism click here.
Systematic name: germacradienol geosmin-lyase (acetone forming)
Comments: Requires Mg2+. Geosmin is the cause of the characteristic smell of moist soil. It is a bifunctional enzyme. The N-terminal part of the enzyme is EC 4.2.3.22, germacradienol synthase, and forms germacradienol from farnesyl diphosphate. The C-terminal part of the enzyme catalyses the conversion of germacradienol to geosmin via (1S,4aS,8aS)-1,4a-dimethyl-1,2,3,4,4a,5,6,8a-octahydronaphthalene.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:
References:
1. Jiang, J., He, X. and Cane, D.E. Geosmin biosynthesis. Streptomyces coelicolor germacradienol/germacrene D synthase converts farnesyl diphosphate to geosmin. J. Am. Chem. Soc. 128 (2006) 8128-8129. [PMID: 16787064]
2. Cane, D.E., He, X., Kobayashi, S., Omura, S. and Ikeda, H. Geosmin biosynthesis in Streptomyces avermitilis. Molecular cloning, expression, and mechanistic study of the germacradienol/geosmin synthase. J. Antibiot. (Tokyo) 59 (2006) 471-479. [PMID: 17080683]
3. Jiang, J., He, X. and Cane, D.E. Biosynthesis of the earthy odorant geosmin by a bifunctional Streptomyces coelicolor enzyme. Nat. Chem. Biol. 3 (2007) 711-715. [PMID: 17873868]