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MetaCyc Pathway: geosmin biosynthesis
Inferred from experiment

Enzyme View:

Pathway diagram: geosmin biosynthesis

This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Superclasses: BiosynthesisSecondary Metabolites BiosynthesisTerpenoids BiosynthesisSesquiterpenoids Biosynthesis

Some taxa known to possess this pathway include : Myxococcus xanthus, Stigmatella aurantiaca, Streptomyces coelicolor

Expected Taxonomic Range: Cyanobacteria, Fungi, Marchantiophyta, Myxococcales, Streptomycetaceae

Geosmin is the substrate that gives fresh moist soil its typical "earthy" smell. When present in water, wine or fish, it conveyes an undesirable muddy flavor. The human taste buds are very sensitive to geosmin, and can detect a concentration as small as 0.7 ppb (parts per billion). Geosmin was first isolated from actinomycetes [Gerber65].

Geosmin is produced by a number of microorganisms, including most Streptomyces strains [Bentley81] and several species of cyanobacteria [Tsuchiya81, Wu91, Saadoun01, Blaha04], myxobacteria [Dickschat05], fungi [Pisarnitskii, La05] and liverworts [Spörle91]. It has been suggested that the distinctive smell of geosmin enables camels to find water in the desert. In return, the animals aid the bacteria by spreading their spores [Simons03].

As is the case of many other secondary metabolites, geosmin is synthesized from (2E,6E)-farnesyl diphosphate (FPP). In Streptomyces coelicolor a single enzyme, geosmin synthase / octalin synthase / germacradienol synthase, catalyzes all steps required. It is a bifunctional enzyme, with its N-terminal domain responsible for converting (2E,6E)-farnesyl diphosphate to (1E,4S,5E,7R)-germacra-1(10),5-dien-11-ol, and the C-terminal domain catalyzing the transformation of (1E,4S,5E,7R)-germacra-1(10),5-dien-11-ol to (-)-geosmin, in a process that generates acetone [Jiang06, Jiang07, Nawrath08]. Both steps require Mg2+.

Created 09-Jun-2008 by Caspi R, SRI International


Bentley81: Bentley R, Meganathan R (1981). "Geosmin and methylisoborneol biosynthesis in streptomycetes. Evidence for an isoprenoid pathway and its absence in non-differentiating isolates." FEBS Lett 125(2);220-2. PMID: 7227551

Blaha04: Blaha L, Sabater S, Babica P, Vilalta E, Marsalek B (2004). "Geosmin occurrence in riverine cyanobacterial mats: is it causing a significant health hazard?." Water Sci Technol 49(9);307-12. PMID: 15237639

Dickschat05: Dickschat JS, Bode HB, Mahmud T, Muller R, Schulz S (2005). "A novel type of geosmin biosynthesis in myxobacteria." J Org Chem 70(13);5174-82. PMID: 15960521

Gerber65: Gerber, N.N., Lecheval, H.A. (1965). "Geosmin an earthy-smelling substance isolated from Actinomycetes." Applied Microbiology 13(6) 935-938.

Jiang06: Jiang J, He X, Cane DE (2006). "Geosmin biosynthesis. Streptomyces coelicolor germacradienol/germacrene D synthase converts farnesyl diphosphate to geosmin." J Am Chem Soc 128(25);8128-9. PMID: 16787064

Jiang07: Jiang J, He X, Cane DE (2007). "Biosynthesis of the earthy odorant geosmin by a bifunctional Streptomyces coelicolor enzyme." Nat Chem Biol 3(11);711-5. PMID: 17873868

Jiang08: Jiang J, Cane DE (2008). "Geosmin biosynthesis. Mechanism of the fragmentation-rearrangement in the conversion of germacradienol to geosmin." J Am Chem Soc 130(2);428-9. PMID: 18095692

La05: La Guerche S, Chamont S, Blancard D, Dubourdieu D, Darriet P (2005). "Origin of (-)-geosmin on grapes: on the complementary action of two fungi, botrytis cinerea and penicillium expansum." Antonie Van Leeuwenhoek 88(2);131-9. PMID: 16096689

Nawrath08: Nawrath T, Dickschat JS, Muller R, Jiang J, Cane DE, Schulz S (2008). "Identification of (8S,9S,10S)-8,10-dimethyl-1-octalin, a key intermediate in the biosynthesis of geosmin in bacteria." J Am Chem Soc 130(2);430-1. PMID: 18095691

Pisarnitskii: Pisarnitskii AF, Egorov IA "[Low molecular weight metabolites produced by various Penicillium species]." Prikl Biokhim Mikrobiol 24(6);760-4. PMID: 3150540

Saadoun01: Saadoun I, Schrader KK, Blevins WT (2001). "Identification of geosmin as a volatile metabolite of Anabaena sp." J Basic Microbiol 41(1);51-5. PMID: 11314247

Simons03: Simons, P. (2003). "Camels act on a hump." The Guardian, Thursday March 6 2003.

Spörle91: Spörle, J., Becker, H., Allen, N.S., Gupta, M.P. (1991). "Occurrence of (-)-geosmin and other terpenoids in an axenic culture of the liverwort Symphyogyna brongniartii." Z. fur Naturfors. C 46, 183-188.

Tsuchiya81: Tsuchiya Y, Matsumoto A, Okamoto T (1981). "[Identification of volatile metabolites produced by blue-green algae, Oscillatoria splendida, O. amoena, O. geminata and Aphanizomenon sp]." Yakugaku Zasshi 101(9);852-6. PMID: 6820045

Wu91: Wu JT, Ma PI, Chou TL (1991). "Variation of geosmin content in Anabaena cells and its relation to nitrogen utilization." Arch Microbiol 157(1);66-9. PMID: 1814277

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Cane03: Cane DE, Watt RM (2003). "Expression and mechanistic analysis of a germacradienol synthase from Streptomyces coelicolor implicated in geosmin biosynthesis." Proc Natl Acad Sci U S A 100(4);1547-51. PMID: 12556563

Cane06: Cane DE, He X, Kobayashi S, Omura S, Ikeda H (2006). "Geosmin biosynthesis in Streptomyces avermitilis. Molecular cloning, expression, and mechanistic study of the germacradienol/geosmin synthase." J Antibiot (Tokyo) 59(8);471-9. PMID: 17080683

Gust03: Gust B, Challis GL, Fowler K, Kieser T, Chater KF (2003). "PCR-targeted Streptomyces gene replacement identifies a protein domain needed for biosynthesis of the sesquiterpene soil odor geosmin." Proc Natl Acad Sci U S A 100(4);1541-6. PMID: 12563033

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Sun May 1, 2016, biocyc14.