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 FPP. 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.
conversion of germacradienol to geosmin results in the release of the three-carbon side chain as acetone and involves a 1,2-hydride shift of the bridgehead hydrogen exclusively into ring B of geosmin
the active site in the N-terminal domain of enzyme ScGS catalyzes the ionization-dependent cyclization of FPP to form diphosphate and two cyclic products: germacradienol (major product, 85%) and germacrene D (minor product, 15%). After dissociation from the N-terminal domain, germacradienol is rebound to the active site of the C-terminal domain where it is converted to geosmin in a protonation-dependent cyclization reaction accompanied by the elimination of acetone through a retro-Prins reaction. The tandem cyclization-fragmentation reactions catalyzed by ScGS require two distinct active sites, a unique alphaalpha domain architecture is predicted for ScGS based on primary structure analysis
the active site in the N-terminal domain of enzyme ScGS catalyzes the ionization-dependent cyclization of FPP to form diphosphate and two cyclic products: germacradienol (major product, 85%) and germacrene D (minor product, 15%). After dissociation from the N-terminal domain, germacradienol is rebound to the active site of the C-terminal domain where it is converted to geosmin in a protonation-dependent cyclization reaction accompanied by the elimination of acetone through a retro-Prins reaction. The tandem cyclization-fragmentation reactions catalyzed by ScGS require two distinct active sites, a unique alphaalpha domain architecture is predicted for ScGS based on primary structure analysis
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SYSTEMATIC NAME
IUBMB Comments
germacradienol geosmin-lyase (acetone forming)
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 FPP. 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.
presence of Mg2+, synthesis of 66% (4S,7R)-germacra-1(10)E,5E-diene-11-ol, 24% (7S)-germacrene D, 8% geosmin, and 2% of a hydrocarbon, tentatively assigned the structure of octalin
conversion of germacradienol to geosmin results in the release of the three-carbon side chain as acetone and involves a 1,2-hydride shift of the bridgehead hydrogen exclusively into ring B of geosmin
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. The enzyme has an alpha,alpha domain architecture, each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg2+ for catalysis. There is no direct channel for transfer of the intermediate from the active site of the N-terminal domain to that of the C-terminal domain. It is a diiffusive transfer of the germacradienol intermediate
geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. The enzyme has an alpha,alpha domain architecture, each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg2+ for catalysis. There is no direct channel for transfer of the intermediate from the active site of the N-terminal domain to that of the C-terminal domain. It is a diiffusive transfer of the germacradienol intermediate
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
geosmin synthase from Streptomyces coelicolor (ScGS) catalyzes an unusual, metal-dependent terpenoid cyclization and fragmentation reaction sequence. Two distinct active sites are required for catalysis: the N-terminal domain catalyzes the ionization and cyclization of farnesyl diphosphate to form germacradienol and inorganic pyrophosphate (PPi), and the C-terminal domain catalyzes the protonation, cyclization, and fragmentation of germacradienol to form geosmin and acetone through a retro-Prins reaction. The enzyme has an alpha,alpha domain architecture, each domain contains the metal-binding motifs typical of a class I terpenoid cyclase, and each domain requires Mg2+ for catalysis. There is no direct channel for transfer of the intermediate from the active site of the N-terminal domain to that of the C-terminal domain. It is a diiffusive transfer of the germacradienol intermediate
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
geosmin synthase is a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
i.e. ANA318, isolated at the Australian Water Quality Centre in 1995 from a sample sourced from Pejar Dam in Goulburn, NSW, Australia, during a taste and odor episode
i.e. ANA318, isolated at the Australian Water Quality Centre in 1995 from a sample sourced from Pejar Dam in Goulburn, NSW, Australia, during a taste and odor episode
relative enzyme expression analysis, enzyme expression under conditions of continuous light illumination and the removal of light as a stimulus appears to be constitutive, the decrease in geosmin synthase transcription post maximum cell numbers and stationary phase suggests that a decrease in isoprenoid synthesis may occur before a decrease in the transcription of ribosomal units as the process of cell death is initiated
relative enzyme expression analysis, enzyme expression under conditions of continuous light illumination and the removal of light as a stimulus appears to be constitutive, the decrease in geosmin synthase transcription post maximum cell numbers and stationary phase suggests that a decrease in isoprenoid synthesis may occur before a decrease in the transcription of ribosomal units as the process of cell death is initiated
the enzyme is one of only three type I terpene synthases (TSs, sce1440, sce6369, sce8552) and one type II TS (sce4636), responsible for the production of at least 17 sesquiterpenes in Sorangium cellulosum
the enzyme is one of only three type I terpene synthases (TSs, sce1440, sce6369, sce8552) and one type II TS (sce4636), responsible for the production of at least 17 sesquiterpenes in Sorangium cellulosum
deletion of the doxorubicin gene cluster results in increased cell growth rate along with detectable production of geosmin. Overexpression of the spterp13 gene in the Streptomyecs peucetius doxorubicin mutant leads to 2.4fold enhanced production of geosmin
geosmin is a powerful odorant with an extremely low human detection threshold of less than 10 parts-per-trillion, and is mainly responsible for the characteristic odor of freshly turned earth. Although geosmin contributes to the pleasant, earthy flavor of beets, it is also a commonly occurring contaminant of musty-tasting water, wine, and fish. Geosmin is not known to cause human disease, but its detection and elimination from potable water sources is a critical environmental and water quality issue
the enzyme is responsible for geosmin biosynthesis. Geosmin is a secondary metabolite responsible for earthy odors. The occurrence of geosmin has great impact on the quality of water environment. Analysis of the geosmin production under d ifferent environments
geosmin is a powerful odorant with an extremely low human detection threshold of less than 10 parts-per-trillion, and is mainly responsible for the characteristic odor of freshly turned earth. Although geosmin contributes to the pleasant, earthy flavor of beets, it is also a commonly occurring contaminant of musty-tasting water, wine, and fish. Geosmin is not known to cause human disease, but its detection and elimination from potable water sources is a critical environmental and water quality issue
the enzyme is responsible for geosmin biosynthesis. Geosmin is a secondary metabolite responsible for earthy odors. The occurrence of geosmin has great impact on the quality of water environment. Analysis of the geosmin production under d ifferent environments
neither full-length ScGS nor constructs of the C-terminal domain can be crystallized, but homology models of the C-terminal domain are constructed based on about 36% sequence identity with the N-terminal domain, analysis of the crystal structure of the N-terminal domain in unliganded or liganded form, overview. Possible alpha,alpha domain architectures as frameworks for bifunctional catalysis
neither full-length ScGS nor constructs of the C-terminal domain can be crystallized, but homology models of the C-terminal domain are constructed based on about 36% sequence identity with the N-terminal domain, analysis of the crystal structure of the N-terminal domain in unliganded or liganded form, overview. Possible alpha,alpha domain architectures as frameworks for bifunctional catalysis
neither full-length ScGS nor constructs of the C-terminal domain can be crystallized, but homology models of the C-terminal domain are constructed based on about 36% sequence identity with the N-terminal domain, analysis of the crystal structure of the N-terminal domain in unliganded or liganded form, overview. Possible alpha,alpha domain architectures as frameworks for bifunctional catalysis
geosmin synthase has alpha-alpha domain architecture. The N-terminal domain and the C-terminal domain are separated by a 41-residue linker and share 28% and 29% amino acid sequence identity, respectively, with pentalenene synthase. Each domain contains characteristic metal ion-binding motifs of class I terpenoid cyclases. The aspartate-rich motif is found as D86DHFLE91 and D455DYYP459, and the NSE/DTE motif is found as N229DLFSYQRE237 and N598DVFSYQKE606. The C-terminal domain is also predicted to adopt an alpha fold homologous to that of the N-terminal domain based on approximately 36% amino acid sequence identity between these domains. Primary, secondary and quarternary enzyme structrue analysis, and homology modeling, overview
geosmin synthase has alpha-alpha domain architecture. The N-terminal domain and the C-terminal domain are separated by a 41-residue linker and share 28% and 29% amino acid sequence identity, respectively, with pentalenene synthase. Each domain contains characteristic metal ion-binding motifs of class I terpenoid cyclases. The aspartate-rich motif is found as D86DHFLE91 and D455DYYP459, and the NSE/DTE motif is found as N229DLFSYQRE237 and N598DVFSYQKE606. The C-terminal domain is also predicted to adopt an alpha fold homologous to that of the N-terminal domain based on approximately 36% amino acid sequence identity between these domains. Primary, secondary and quarternary enzyme structrue analysis, and homology modeling, overview
geosmin synthase has alpha-alpha domain architecture. The N-terminal domain and the C-terminal domain are separated by a 41-residue linker and share 28% and 29% amino acid sequence identity, respectively, with pentalenene synthase. Each domain contains characteristic metal ion-binding motifs of class I terpenoid cyclases. The aspartate-rich motif is found as D86DHFLE91 and D455DYYP459, and the NSE/DTE motif is found as N229DLFSYQRE237 and N598DVFSYQKE606. The C-terminal domain is also predicted to adopt an alpha fold homologous to that of the N-terminal domain based on approximately 36% amino acid sequence identity between these domains. Primary, secondary and quarternary enzyme structrue analysis, and homology modeling, overview
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
purified recombinant N-terminal domain of ScGS, unliganded and in complex with 3 Mg2+ ions and alendronate, mixing of 600 nl of 7 mg/ml protein in 25 mM Tris, pH 8.2, 5 mM MgCl2, 10 mM BME, and 1.5 mM sodium alendronate, with 600 nl of precipitant solution containing 0.2 M sodium acetate trihydrate, pH 7.0, and 20% w/v PEG 3350, and equilibration against 0.1 ml of reservoir solution at room temperature, X-ray diffraction structure determination and analysis at 2.4 A resolution. Neither full-length ScGS nor constructs of the C-terminal domain can be crystallized, but homology models of the C-terminal domain are constructed based on about 36% sequence identity with the N-terminal domain
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PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
recombinant C-terminally His6-tagged full-length enzyme from Escherichia coli strain BL21(DE3)pLysS by nickel affinity chromatography, recombinant N-terminal domain of ScGS (residues 1-366) from Escherichia coli strain BL21(DE3)pLysS by ammonium sulfate fractionation, adsorption chromatography on methyl resin, gel filtration, and ultrafiltartion
gene cyc2, recombinant expression of C-terminally His6-tagged full-length enzyme and of the N-terminal domain of ScGS (residues 1-366) in Escherichia coli strain BL21(DE3)pLysS , subcloning in Escherichia coli strain XL-1 Blue
gene geo, cloning of full-length of geosmin synthase gene from Aphanizomenon gracile strain WH-1, DNA and amino acid sequence determination and analysis, phylogenetic tree, real time PCR is applied to quantify the geosmin production in different light and temperature. Low temperature (15°C), high light intensity (0.035 mmol/s/m) and continuous light illumination are beneficial to the expression of geo. The successful amplification of geosmin synthase gene verifies that hiTAIL-PCR is an effective and simple procedure of low cost
Structural studies of geosmin synthase, a bifunctional sesquiterpene synthase with alpha-alpha domain architecture that catalyzes a unique cyclization fragmentation reaction sequence
Enzyme Nomenclature
4.1.99.16 geosmin synthase
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