Enzymes
UniProtKB help_outline | 2 proteins |
Enzyme class help_outline |
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GO Molecular Function help_outline |
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Reaction participants Show >> << Hide
- Name help_outline (2E)-geranyl diphosphate Identifier CHEBI:58057 (Beilstein: 4549979) help_outline Charge -3 Formula C10H17O7P2 InChIKeyhelp_outline GVVPGTZRZFNKDS-JXMROGBWSA-K SMILEShelp_outline CC(C)=CCC\C(C)=C\COP([O-])(=O)OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 59 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline H2O Identifier CHEBI:15377 (Beilstein: 3587155; CAS: 7732-18-5) help_outline Charge 0 Formula H2O InChIKeyhelp_outline XLYOFNOQVPJJNP-UHFFFAOYSA-N SMILEShelp_outline [H]O[H] 2D coordinates Mol file for the small molecule Search links Involved in 6,048 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline diphosphate Identifier CHEBI:33019 (Beilstein: 185088) help_outline Charge -3 Formula HO7P2 InChIKeyhelp_outline XPPKVPWEQAFLFU-UHFFFAOYSA-K SMILEShelp_outline OP([O-])(=O)OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 1,085 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline sabinene hydrate Identifier CHEBI:16377 (CAS: 15537-55-0,546-79-2) help_outline Charge 0 Formula C10H18O InChIKeyhelp_outline KXSDPILWMGFJMM-UHFFFAOYSA-N SMILEShelp_outline CC(C)C12CCC(C)(O)C1C2 2D coordinates Mol file for the small molecule Search links Involved in 1 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:19565 | RHEA:19566 | RHEA:19567 | RHEA:19568 | |
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Reaction direction help_outline | undefined | left-to-right | right-to-left | bidirectional |
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Publications
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Monoterpene biosynthesis: demonstration of a geranyl pyrophosphate:sabinene hydrate cyclase in soluble enzyme preparations from sweet marjoram (Majorana hortensis).
Hallahan T.W., Croteau R.
A soluble enzyme preparation from the leaves of sweet marjoram (Majorana hortensis Moench) catalyzes the divalent cation-dependent cyclization of [1-3H]geranyl pyrophosphate to the bicyclic monoterpene alcohols (+)-[6-3H]cis- and (+)-[6-3H]-transsabinene hydrate, providing labeling patterns consis ... >> More
A soluble enzyme preparation from the leaves of sweet marjoram (Majorana hortensis Moench) catalyzes the divalent cation-dependent cyclization of [1-3H]geranyl pyrophosphate to the bicyclic monoterpene alcohols (+)-[6-3H]cis- and (+)-[6-3H]-transsabinene hydrate, providing labeling patterns consistent with current mechanistic considerations. No free intermediates were detectable in the conversion of geranyl pyrophosphate to the sabinene hydrates as determined by isotopic dilution experiments. Label from H2(18)O water was quantitatively incorporated into the products, indicating that the hydroxyl oxygen atoms of both cis- and trans-sabinene hydrate are derived from water and not from the pyrophosphate ester moiety of the substrate. The two enzymatic activities were inseparable by several chromatographic procedures, and differential inactivation studies suggested that the two activities reside with the same enzyme. The sabinene hydrate cyclase (synthase) has an apparent molecular weight of 56,000, shows a pH optimum near 7.0, and requires a divalent metal ion (either Mn2+ or Mg2+) for activity. The enzyme preparation is also capable of cyclizing neryl pyrophosphate, the cis-isomer of geranyl pyrophosphate, and analysis of mixed substrate incubations indicated that the two precursors are mutually competitive. Kinetic analysis and comparison of Vrel/Km values revealed that geranyl pyrophosphate is the more efficient substrate. This is the first report on an enzyme preparation capable of cyclizing geranyl pyrophosphate and neryl pyrophosphate to the isomeric sabinene hydrates. << Less
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Monoterpene biosynthesis: mechanism and stereochemistry of the enzymatic cyclization of geranyl pyrophosphate to (+)-cis- and (+)-trans-sabinene hydrate.
Hallahan T.W., Croteau R.
The conversion of geranyl pyrophosphate to (+)-cis- and (+)-trans-sabinene hydrate by a partially purified cyclase from sweet marjoram (Majorana hortensis) is considered to proceed by the initial ionization and isomerization of the substrate to (-)-(3R)-linalyl pyrophosphate and the subsequent cyc ... >> More
The conversion of geranyl pyrophosphate to (+)-cis- and (+)-trans-sabinene hydrate by a partially purified cyclase from sweet marjoram (Majorana hortensis) is considered to proceed by the initial ionization and isomerization of the substrate to (-)-(3R)-linalyl pyrophosphate and the subsequent cyclization of this enzyme-bound tertiary allylic intermediate to the monocyclic (+)-(4R)-alpha-terpinyl cation. A 1,2-hydride shift and a second cyclization with water capture of the resulting cation complete the reaction sequence. [6-3H, 14C]Geranyl pyrophosphate, coupled with selective chemical degradation of the resulting sabinene hydrate products, was employed to demonstrate the hydride shift, while separate testing of the linalyl pyrophosphate enantiomers confirmed the involvement of the (3R)-antipode in the cyclization and indicated the cyclization of linalyl pyrophosphate to be faster than the coupled isomerization-cyclization of the geranyl substrate. (1R)- and (1S)-[1-3H, 14C]geranyl pyrophosphates, in conjunction with stereoselective degradations of the biosynthetic products to locate the 3H, were exploited to deduce that configuration at C1 of the substrate was retained in the reaction. These findings suggest the isomerization of the geranyl substrate to be a suprafacial process and the cyclization of the (3R)-linalyl intermediate to proceed via the anti,endo-conformation consistent with the stereo-chemistry of other monoterpene cyclizations and with chemical model studies. Sulfonium ion analogs of the presumptive linalyl and alpha-terpinyl cationic intermediates of the isomerization-cyclization sequence were shown to be potent inhibitors of the enzymatic reaction (Ki = 0.3 and 2.8 microM, respectively), and inhibition was synergized by the presence of inorganic pyrophosphate, indicating that the enzyme recognized and bound more tightly to these ion-paired species than to either cationic or anionic partner alone. Additionally, the enzyme was capable of ionizing (solvolyzing) the noncyclizable substrate analogs 6,7-dihydrogeranyl pyrophosphate and 2,3-methanogeranyl pyrophosphate. These results define the overall stereochemistry of the coupled isomerization-cyclization to sabinene hydrate, demonstrate the 1,2-hydride shift, and confirm the electrophilic nature of this enzymatic reaction type. << Less