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Information on EC 7.2.1.3 - ascorbate ferrireductase (transmembrane) and Organism(s) Homo sapiens and UniProt Accession Q53TN4

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IUBMB Comments
A diheme cytochrome that transfers electrons across a single membrane, such as the outer membrane of the enterocyte, or the tonoplast membrane of the plant cell vacuole. Acts on hexacyanoferrate(III) and other ferric chelates.
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This record set is specific for:
Homo sapiens
UNIPROT: Q53TN4
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The taxonomic range for the selected organisms is: Homo sapiens
The enzyme appears in selected viruses and cellular organisms
Synonyms
cytochrome b561, cytochrome b-559, dcytb, ferric chelate reductase, duodenal cytochrome b, cybrd1, cyt b561, cyb561, cyt-b561, lcytb, more
SYNONYM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
cytochrome b reductase 1
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ascorbate-cytochrome b5 reductase
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-
-
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ascorbate-dependent ferrireductase
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CGCytb
chromaffin granule CYB561
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chromaffin granule cytochrome b
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Cybrd1
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Cyt b561
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DCytb
duodenal cytochrome b
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duodenal cytochrome b reductase 1
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ferric reductase
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LCytb
lysosomal cytochrome b
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-
REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
ascorbate[side 1] + Fe(III)[side 2] = monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
reaction mechanism
REACTION TYPE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
redox reaction
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-
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oxidation
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-
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reduction
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-
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SYSTEMATIC NAME
IUBMB Comments
Fe(III):ascorbate oxidorectuctase (electron-translocating)
A diheme cytochrome that transfers electrons across a single membrane, such as the outer membrane of the enterocyte, or the tonoplast membrane of the plant cell vacuole. Acts on hexacyanoferrate(III) and other ferric chelates.
CAS REGISTRY NUMBER
COMMENTARY hide
37237-57-3
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SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
ascorbate[side 1] + Fe(CN)3[side 2]
monodehydroascorbate[side 1] + ?
show the reaction diagram
-
-
-
-
?
ascorbate[side 1] + Fe(III)[side 2]
monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
ascorbate[side 1] + Fe3+-EDTA[side 2]
monodehydroascorbate[side 1] + ?
show the reaction diagram
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-
-
-
?
ascorbate[side 1] + nitroblue tetrazolium[side 2]
dehydroascorbate + ?
show the reaction diagram
-
-
-
-
?
additional information
?
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the other heme-b center is responsible for the ascorbate oxidation by iozyme CGCytb. Structure-function relationship, overview
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-
?
NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
ascorbate[side 1] + Fe(III)[side 2]
monodehydroascorbate[side 1] + Fe(II)[side 2]
show the reaction diagram
-
-
-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
heme
each monomer of the homodimeric protein possesses cytoplasmic and apical heme groups
ascorbate
cytochrome b561
a CYB561 protein
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heme
-
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heme b
two heme-b centers and CYB561 protein, structure analysis and comparisons, overview. Midpoint redox potentials, spin, and spectra of heme b, comparisons
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
Zn2+
1 mM, 43% residual activity. Zn2+ coordinates to two hydroxyl groups of the apical ascorbate and to a histidine residue. Fe3+ competes with Zn2+ for this binding site
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
L-galactono-gamma-lactone
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-
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
the rate of reduction of CYB561 by ascorbate is only slightly pH-dependent, steady-state reduction kinetics
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
-
UniProt
Manually annotated by BRENDA team
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
CGCytb, the chromaffin granule CYB561 of the mammalian adrenal glands (CGCytb) makes up about 10-15% of the adrenal gland chromaffin granule membrane proteins
Manually annotated by BRENDA team
a transmembrane enzyme, localization of both the N- and C-termini of CGCytb in the cytoplasm. Native CGCytb is a transmembrane electron transferring protein that has 6 transmembrane domains with two pairs of His residues, arranged on four consecutive transmembrane domains (the CYB561-core), for coordinating two b-type hemes, one on each side of the membrane, transmembrane orientation, modeling
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
the enzyme is a member of the CYB561 protein family
physiological function
b-type cytochromes are heme-containing, electron-transporting proteins in which the redox active center(s) is (are) iron-protoporphyrin(s) IX non-covalently bound to the protein matrix. Some of the b-type cytochromes are localized in membranous structures and have two heme-b prosthetic groups, the major function of these proteins is transmembrane electron transport. Isozyme DCytb is capable of reducing ferric chelates and plays an important role in the iron acquisition of cells
additional information
the binding sites for the ascorbate on the cytoplasmic and the monodehydroascorbate on the non-cytoplasmic side do not correspond to the putative binding sites that had been inferred from the sequence (homology) analysis as well as from site directed mutagenesis of a number of CYB561 proteins. Models for the sidedness of CYB561 enzymes and the reduction by ascorbate, overview. Importance of an Arg residue in the reduction of rCGCytb
UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION?
CYBR1_HUMAN
286
6
31641
Swiss-Prot
Secretory Pathway (Reliability: 1)
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
Cytb561 enzyme structure analysis, structure-function relationship, detailed overview
CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
enzyme and its complex with ascorbate and Zn2+. Each monomer of the homodimeric protein possesses cytoplasmic and apical heme groups, as well as cytoplasmic and apical ascorbate-binding sites located adjacent to each heme. Zn2+ coordinates to two hydroxyl groups of the apical ascorbate and to a histidine residue. Fe3+ competes with Zn2+ for this binding site
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
F184A
35% residual activity
F58L
less than 50% residual activity
H108A
20% residual activity
H108Q
25% residual activity
Y117A
35% residual activity
Y117S
40% residual activity
Y131L
less than 50% residual activity
H120A
site-directed mutagenesis of DCytb, the mutation results in partial loss of hemes
H159A
site-directed mutagenesis of DCytb, the mutation results in partial loss of hemes
H33A
site-directed mutagenesis, mutation in human DCytb does not influence the physicochemical properties of protein as compared to the wild-type
H50A
site-directed mutagenesis of DCytb, the mutation results in complete loss of hemes
H50A/H120A
site-directed mutagenesis of DCytb, the mutant contains one heme-b per double His-mutant rDCytb
H86A
site-directed mutagenesis of DCytb, the mutation results in complete loss of hemes
H86A/H159A
site-directed mutagenesis of DCytb, the mutant contains one heme-b per double His-mutant rDCytb
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
recombinant C-terminally His6-tagged isozyme DCytb from Spodoptera frugiperda Sf9 cells, and untagged, apoform or fully functional isozyme DCytb from Escherichia coli, to homogeneity
CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
expression in Escherichia coli
expressed in a Saccharomyces cerevisiae strain S288C DELTAfre1DELTAfre2 mutant, which lacks almost all of its plasma membrane ferrireductase activity
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recombinant expression of C-terminally His6-tagged isozyme DCytb in Spodoptera frugiperda Sf9 cells, untagged, apoform or fully functional isozyme DCytb in Escherichia coli
EXPRESSION
ORGANISM
UNIPROT
LITERATURE
iron-deficient patients have significantly higher ferric reductase activity and duodenal and plasma ascorbate concentrations than do control subjects
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REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Su, D.; Asard, H.
Three mammalian cytochromes b561 are ascorbate-dependent ferrireductases
FEBS J.
273
3722-3734
2006
Homo sapiens, Mus musculus, Rattus norvegicus
Manually annotated by BRENDA team
Atanasova, B.D.; Li, A.C.; Bjarnason, I.; Tzatchev, K.N.; Simpson, R.J.
Duodenal ascorbate and ferric reductase in human iron deficiency
Am. J. Clin. Nutr.
81
130-133
2005
Homo sapiens
Manually annotated by BRENDA team
Berczi, A.; Zimanyi, L.
The trans-membrane cytochrome b561 proteins structural information and biological function
Curr. Protein Pept. Sci.
15
745-760
2014
Bos taurus (P10897), Homo sapiens (P49447), Schistosoma japonicum (Q5D8X4), Zea mays (Q6I681), Mus musculus (Q6P1H1), Arabidopsis thaliana (Q9SWS1)
Manually annotated by BRENDA team
Ganasen, M.; Togashi, H.; Takeda, H.; Asakura, H.; Tosha, T.; Yamashita, K.; Hirata, K.; Nariai, Y.; Urano, T.; Yuan, X.; Hamza, I.; Mauk, A.G.; Shiro, Y.; Sugimotom, H.; Sawai, H.
Structural basis for promotion of duodenal iron absorption by enteric ferric reductase with ascorbate
Commun. Biol.
1
120
2018
Homo sapiens (Q53TN4), Homo sapiens
Manually annotated by BRENDA team