Enzymes
UniProtKB help_outline | 1,754 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 Fe3+ Identifier CHEBI:29034 (CAS: 20074-52-6) help_outline Charge 3 Formula Fe InChIKeyhelp_outline VTLYFUHAOXGGBS-UHFFFAOYSA-N SMILEShelp_outline [Fe+3] 2D coordinates Mol file for the small molecule Search links Involved in 233 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline L-ascorbate Identifier CHEBI:38290 (Beilstein: 3549814; CAS: 299-36-5) help_outline Charge -1 Formula C6H7O6 InChIKeyhelp_outline CIWBSHSKHKDKBQ-JLAZNSOCSA-M SMILEShelp_outline [H][C@@]1(OC(=O)C(O)=C1[O-])[C@@H](O)CO 2D coordinates Mol file for the small molecule Search links Involved in 34 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline Fe2+ Identifier CHEBI:29033 (CAS: 15438-31-0) help_outline Charge 2 Formula Fe InChIKeyhelp_outline CWYNVVGOOAEACU-UHFFFAOYSA-N SMILEShelp_outline [Fe++] 2D coordinates Mol file for the small molecule Search links Involved in 249 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- 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 9,134 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
- Name help_outline monodehydro-L-ascorbate radical Identifier CHEBI:59513 Charge -1 Formula C6H6O6 InChIKeyhelp_outline LHFJOBMTAJJOTB-JLAZNSOCSA-M SMILEShelp_outline [H][C@@]1(OC(=O)C([O-])=C1[O])[C@@H](O)CO 2D coordinates Mol file for the small molecule Search links Involved in 16 reaction(s) Find molecules that contain or resemble this structure Find proteins in UniProtKB for this molecule
Cross-references
RHEA:30403 | RHEA:30404 | RHEA:30405 | RHEA:30406 | |
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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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An iron-regulated ferric reductase associated with the absorption of dietary iron.
McKie A.T., Barrow D., Latunde-Dada G.O., Rolfs A., Sager G., Mudaly E., Mudaly M., Richardson C., Barlow D., Bomford A., Peters T.J., Raja K.B., Shirali S., Hediger M.A., Farzaneh F., Simpson R.J.
The ability of intestinal mucosa to absorb dietary ferric iron is attributed to the presence of a brush-border membrane reductase activity that displays adaptive responses to iron status. We have isolated a complementary DNA, Dcytb (for duodenal cytochrome b), which encoded a putative plasma membr ... >> More
The ability of intestinal mucosa to absorb dietary ferric iron is attributed to the presence of a brush-border membrane reductase activity that displays adaptive responses to iron status. We have isolated a complementary DNA, Dcytb (for duodenal cytochrome b), which encoded a putative plasma membrane di-heme protein in mouse duodenal mucosa. Dcytb shared between 45 and 50% similarity to the cytochrome b561 family of plasma membrane reductases, was highly expressed in the brush-border membrane of duodenal enterocytes, and induced ferric reductase activity when expressed in Xenopus oocytes and cultured cells. Duodenal expression levels of Dcytb messenger RNA and protein were regulated by changes in physiological modulators of iron absorption. Thus, Dcytb provides an important element in the iron absorption pathway. << Less
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Dcytb (Cybrd1) functions as both a ferric and a cupric reductase in vitro.
Wyman S., Simpson R.J., McKie A.T., Sharp P.A.
MDCK cells expressing an inducible duodenal cytochrome b-green fluorescent protein (Dcytb-EGFP) fusion construct were used to investigate the function of Dcytb. The Dcytb-EGFP protein was targeted correctly to the plasma membrane, and cells displayed increased ferric and cupric reductase activitie ... >> More
MDCK cells expressing an inducible duodenal cytochrome b-green fluorescent protein (Dcytb-EGFP) fusion construct were used to investigate the function of Dcytb. The Dcytb-EGFP protein was targeted correctly to the plasma membrane, and cells displayed increased ferric and cupric reductase activities, which were greatly reduced in the presence of doxycycline. The data suggests that Dcytb plays a physiological role in both iron and copper uptake, through divalent metal transporter 1 (DMT1) and copper transporter 1, respectively. In support of this hypothesis, we show that 59Fe uptake was significantly enhanced in Dcytb-EGFP expressing MDCK cells which endogenously express DMT1. << Less
FEBS Lett. 582:1901-1906(2008) [PubMed] [EuropePMC]
This publication is cited by 1 other entry.
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Three mammalian cytochromes b561 are ascorbate-dependent ferrireductases.
Su D., Asard H.
Cytochromes b(561) are a family of transmembrane proteins found in most eukaryotic cells. Three evolutionarily closely related mammalian cytochromes b(561) (chromaffin granule cytochrome b, duodenal cytochrome b, and lysosomal cytochrome b) were expressed in a Saccharomyces cerevisiaeDeltafre1Delt ... >> More
Cytochromes b(561) are a family of transmembrane proteins found in most eukaryotic cells. Three evolutionarily closely related mammalian cytochromes b(561) (chromaffin granule cytochrome b, duodenal cytochrome b, and lysosomal cytochrome b) were expressed in a Saccharomyces cerevisiaeDeltafre1Deltafre2 mutant, which lacks almost all of its plasma membrane ferrireductase activity, to study their ability to reduce ferric iron (Fe(3+)). The expression of each of these cytochromes b(561) was able to rescue the growth defect of the Deltafre1Deltafre2 mutant cells in iron-deficient conditions, suggesting their involvement in iron metabolism. Plasma membrane ferrireductase activities were measured using intact yeast cells. Each cytochrome b(561) showed significant FeCN and Fe(3+)-EDTA reductase activities that were dependent on the presence of intracellular ascorbate. Site-directed mutagenesis of lysosomal cytochrome b was conducted to identify amino acids that are indispensable for its activity. Among more than 20 conserved or partially conserved amino acids that were investigated, mutations of four His residues (H47, H83, H117 and H156), one Tyr (Y66) and one Arg (R67) completely abrogated the FeCN reductase activity, whereas mutations of Arg (R149), Phe (F44), Ser (S115), Trp (W119), Glu (E196), and Gln (Q131) affected the ferrireductase activity to some degree. These mutations may affect the heme coordination, ascorbate binding, and/or ferric substrate binding. Possible roles of these residues in lysosomal cytochrome b are discussed. This study demonstrates the ascorbate-dependent transmembrane ferrireductase activities of members of the mammalian cytochrome b(561) family of proteins. << Less
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Structure and mechanism of a eukaryotic transmembrane ascorbate-dependent oxidoreductase.
Lu P., Ma D., Yan C., Gong X., Du M., Shi Y.
Vitamin C, also known as ascorbate, is required in numerous essential metabolic reactions in eukaryotes. The eukaryotic ascorbate-dependent oxidoreductase cytochrome b561 (Cyt b561), a family of highly conserved transmembrane enzymes, plays an important role in ascorbate recycling and iron absorpt ... >> More
Vitamin C, also known as ascorbate, is required in numerous essential metabolic reactions in eukaryotes. The eukaryotic ascorbate-dependent oxidoreductase cytochrome b561 (Cyt b561), a family of highly conserved transmembrane enzymes, plays an important role in ascorbate recycling and iron absorption. Although Cyt b561 was identified four decades ago, its atomic structure and functional mechanism remain largely unknown. Here, we report the high-resolution crystal structures of cytochrome b561 from Arabidopsis thaliana in both substrate-free and substrate-bound states. Cyt b561 forms a homodimer, with each protomer consisting of six transmembrane helices and two heme groups. The negatively charged substrate ascorbate, or monodehydroascorbate, is enclosed in a positively charged pocket on either side of the membrane. Two highly conserved amino acids, Lys(81) and His(106), play an essential role in substrate recognition and catalysis. Our structural and biochemical analyses allow the proposition of a general electron transfer mechanism for members of the Cyt b561 family. << Less
Proc. Natl. Acad. Sci. U.S.A. 111:1813-1818(2014) [PubMed] [EuropePMC]
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Cytochrome b 561 of the bovine adrenal chromaffin granules. A high potential b-type cytochrome.
Flatmark T., Terland O.