Enzymes
| UniProtKB help_outline | 4 proteins |
| Enzyme class help_outline |
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| GO Molecular Function help_outline |
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- Name help_outline H+ Identifier CHEBI:15378 Charge 1 Formula H InChIKeyhelp_outline GPRLSGONYQIRFK-UHFFFAOYSA-N SMILEShelp_outline [H+] 2D coordinates Mol file for the small molecule Search links Involved in 9,431 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline homogentisate Identifier CHEBI:16169 (Beilstein: 3668593) help_outline Charge -1 Formula C8H7O4 InChIKeyhelp_outline IGMNYECMUMZDDF-UHFFFAOYSA-M SMILEShelp_outline Oc1ccc(O)c(CC([O-])=O)c1 2D coordinates Mol file for the small molecule Search links Involved in 9 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline phytyl diphosphate Identifier CHEBI:75434 Charge -3 Formula C20H39O7P2 InChIKeyhelp_outline ITPLBNCCPZSWEU-PYDDKJGSSA-K SMILEShelp_outline CC(C)CCC[C@@H](C)CCC[C@@H](C)CCC\C(C)=C\COP([O-])(=O)OP([O-])([O-])=O 2D coordinates Mol file for the small molecule Search links Involved in 8 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline 2-methyl-6-phytyl-1,4-benzene-1,4-diol Identifier CHEBI:75920 Charge 0 Formula C27H46O2 InChIKeyhelp_outline GTWCNYRFOZKWTL-UOFXASEASA-N SMILEShelp_outline CC(C)CCC[C@@H](C)CCC[C@@H](C)CCC\C(C)=C\Cc1cc(O)cc(C)c1O 2D coordinates Mol file for the small molecule Search links Involved in 3 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline CO2 Identifier CHEBI:16526 (Beilstein: 1900390; CAS: 124-38-9) help_outline Charge 0 Formula CO2 InChIKeyhelp_outline CURLTUGMZLYLDI-UHFFFAOYSA-N SMILEShelp_outline O=C=O 2D coordinates Mol file for the small molecule Search links Involved in 997 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 1,129 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
| RHEA:37975 | RHEA:37976 | RHEA:37977 | RHEA:37978 | |
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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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Vitamin E biosynthesis: functional characterization of the monocot homogentisate geranylgeranyl transferase.
Yang W., Cahoon R.E., Hunter S.C., Zhang C., Han J., Borgschulte T., Cahoon E.B.
The biosynthesis of the tocotrienol and tocopherol forms of vitamin E is initiated by prenylation of homogentisate. Geranylgeranyl diphosphate (GGDP) is the prenyl donor for tocotrienol synthesis, whereas phytyl diphosphate (PDP) is the prenyl donor for tocopherol synthesis. We have previously sho ... >> More
The biosynthesis of the tocotrienol and tocopherol forms of vitamin E is initiated by prenylation of homogentisate. Geranylgeranyl diphosphate (GGDP) is the prenyl donor for tocotrienol synthesis, whereas phytyl diphosphate (PDP) is the prenyl donor for tocopherol synthesis. We have previously shown that tocotrienol synthesis is initiated in monocot seeds by homogentisate geranylgeranyl transferase (HGGT). This enzyme is related to homogentisate phytyltransferase (HPT), which catalyzes the prenylation step in tocopherol synthesis. Here we show that monocot HGGT is localized in the plastid and expressed primarily in seed endosperm. Despite the close structural relationship of monocot HGGT and HPT, these enzymes were found to have distinct substrate specificities. Barley (Hordeum vulgare cv. Morex) HGGT expressed in insect cells was six times more active with GGDP than with PDP, whereas the Arabidopsis HPT was nine times more active with PDP than with GGDP. However, only small differences were detected in the apparent Km values of barley HGGT for GGDP and PDP. Consistent with its in vitro substrate properties, barley HGGT generated a mixture of tocotrienols and tocopherols when expressed in the vitamin E-null vte2-1 mutant lacking a functional HPT. Relative levels of tocotrienols and tocopherols produced in vte2-1 differed between organs and growth stages, reflective of the composition of plastidic pools of GGDP and PDP. In addition, HGGT was able to functionally substitute for HPT to rescue vte2-1-associated phenotypes, including reduced seed viability and increased fatty acid oxidation of seed lipids. Overall, we show that monocot HGGT is biochemically distinct from HPT, but can replace HPT in important vitamin E-related physiological processes. << Less
Plant J. 65:206-217(2011) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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Isolation and functional analysis of homogentisate phytyltransferase from Synechocystis sp. PCC 6803 and Arabidopsis.
Collakova E., DellaPenna D.
Tocopherols, collectively known as vitamin E, are lipid-soluble antioxidants synthesized exclusively by photosynthetic organisms and are required components of mammalian diets. The committed step in tocopherol biosynthesis involves condensation of homogentisic acid and phytyl diphosphate (PDP) cat ... >> More
Tocopherols, collectively known as vitamin E, are lipid-soluble antioxidants synthesized exclusively by photosynthetic organisms and are required components of mammalian diets. The committed step in tocopherol biosynthesis involves condensation of homogentisic acid and phytyl diphosphate (PDP) catalyzed by a membrane-bound homogentisate phytyltransferase (HPT). HPTs were identified from Synechocystis sp. PCC 6803 and Arabidopsis based on their sequence similarity to chlorophyll synthases, which utilize PDP in a similar prenylation reaction. HPTs from both organisms used homogentisic acid and PDP as their preferred substrates in vitro but only Synechocystis sp. PCC 6803 HPT was active with geranylgeranyl diphosphate as a substrate. Neither enzyme could utilize solanesyl diphosphate, the prenyl substrate for plastoquinone-9 synthesis. In addition, disruption of Synechocystis sp. PCC 6803 HPT function causes an absence of tocopherols without affecting plastoquinone-9 levels, indicating that separate polyprenyltransferases exist for tocopherol and plastoquinone synthesis in Synechocystis sp. PCC 6803. It is surprising that the absence of tocopherols in this mutant had no discernible effect on cell growth and photosynthesis. << Less
Plant Physiol. 127:1113-1124(2001) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.