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Enzyme Nomenclature
Information on EC 1.10.3.14 - ubiquinol oxidase (electrogenic, non H+-transporting)
Word Map on EC 1.10.3.14
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The enzyme appears in viruses and cellular organisms
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EC NUMBER 
COMMENTARY 
1.10.3.14
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RECOMMENDED NAME
GeneOntology No.
ubiquinol oxidase (electrogenic, non H+-transporting)
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
2 ubiquinol + O2 + 4 H+[side 1] = 2 ubiquinone + 2 H2O + 4 H+[side 2]
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
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SYSTEMATIC NAME
IUBMB Comments
ubiquinol:O2 oxidoreductase (electrogenic, non H+-transporting)
This terminal oxidase enzyme is unable to pump protons but generates a proton motive force by transmembrane charge separation resulting from utilizing protons and electrons originating from opposite sides of the membrane to generate water. The bioenergetic efficiency (the number of charges driven across the membrane per electron used to reduce oxygen to water) is 1. The bd-I oxidase from the bacterium Escherichia coli is the predominant respiratory oxygen reductase that functions under microaerophilic conditions in that organism. cf. EC 1.10.3.10, ubiquinol oxidase (H+-transporting).
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
Q9L8R7 i.e. subunit cydA, Q9L8R6 i.e. subunit cydB
Q9L8R7 and Q9L8R6
UniProt
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
physiological function
Q9L8R6, Q9L8R7 and Q9L8R6
inactivation of cydA or cydB by gene disruption results in loss of d-heme absorbance at 631 nm. Inactivation of cydA has no effect on the ability of Mycobacterium smegmatis to exit from stationary phase at 37 or 42°C. No discernible growth defect of the mutant is observed under moderately aerobic conditions, while the mutant displays a significant growth disadvantage when cocultured with the wild type under extreme microaerophilia. The cydA mutant displays a competitive growth disadvantage in the presence of the terminal oxidase inhibitor, cyanide, when cocultured with wild type at 21% air saturation in an oxystat; inactivation of cydA or cydB gene disruption results in loss of d-heme absorbance at 631 nm
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
2 1,4-naphthoquinol + O2 + 4 H+[side 1]
2 1,4-naphthoquinone + 2 H2O + 4 H+[side 2]
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?
2 2,3-dimethoxy-5-methyl-1,4-benzoquinol + O2 + 4 H+[side 1]
2 2,3-dimethoxy-5-methyl-1,4-benzoquinone + 2 H2O + 4 H+[side 2]
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?
2 duroquinol + O2 + 4 H+[side 1]
2 duroquinone + 2 H2O + 4 H+[side 2]
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?
2 menadiol + O2 + 4 H+[side 1]
2 menadione + 2 H2O + 4 H+[side 2]
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?
2 ubiquinol + O2 + 4 H+[side 1]
2 ubiquinone + 2 H2O + 4 H+[side 2]
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?
2 ubiquinol + O2 + 4 H+[side 1]
2 ubiquinone + 2 H2O + 4 H+[side 2]
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respiratory terminal oxidase
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additional information
?
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after the initial binding of O2, the O–O bond is heterolytically cleaved to yield a kinetically competent heme d oxoferryl porphyrin pi-cation radical intermediate magnetically interacting with heme b595. This intermediate accumulates to 0.75-0.85 per enzyme in agreement with its much higher rate of formation at 20000 per s compared with its rate of decay of 1900 per s. The intermediate is next converted to a short lived heme d oxoferryl in a phase kinetically matched to the oxidation of heme b558 before completion of the reaction. The results indicate that cytochrome bd oxidases break the O-O bond in a single four-electron transfer without a peroxide intermediate. The fourth electron is donated by the porphyrin moiety rather than by a nearby amino acid
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additional information
?
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enzyme additionally catalyzes oxidation of N,N,N',N'-tetramethyl-p-phenylenediamine. This reaction is sensitive to inhibition by cyanide
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
2 ubiquinol + O2 + 4 H+[side 1]
2 ubiquinone + 2 H2O + 4 H+[side 2]
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respiratory terminal oxidase
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?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
heme
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heme b558 and the heme b595/heme d complex are likely to be close to each other. All three hemes are predicted to be near the periplasmic surface
heme
Q9L8R6, Q9L8R7 and Q9L8R6
two- to threefold increase in cydAB gene expression upon reduction of the pO2 of the growth medium from 21 to 0.5% air saturation with concomitant increase in d-heme absorbance in spectra of membranes isolated from wild-type Mycobacterium smegmatis cultured at 1% air saturation; two- to threefold increase in cydAB gene expression upon reduction of the pO2 of the growth medium from 21 to 0.5% air saturation with concomitant increase in d-heme absorbance in spectra of membranes isolated from wild-type Mycobacterium smegmatis cultured at 1% air saturation
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SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
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the cytochrome bd-I complexis concentrated in mobile patches in the plasma membrane
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subnit cydA has nine transmembrane helices with the O2 reactive site near the periplasmic surface. Residue His19, the ligand to the high spin heme b595 component of the oxidase, is located near the periplasmic surface of the protein
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
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the purified, enzymatically active cytochrome d complex solubilized in Triton X-100 is an alphabeta heterodimer
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
two- to threefold increase in cydAB gene expression upon reduction of the pO2 of the growth medium from 21 to 0.5% air saturation; two- to threefold increase in cydAB gene expression upon reduction of the pO2 of the growth medium from 21 to 0.5% air saturation
Q9L8R6, Q9L8R7 and Q9L8R6
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
D239A
mutation in subunit cydA. Mutant is not able to confer the ability to grow aerobically to a strain that has no genomically encoded respiratory oxidases. Heme content similar to wild-type, complete loss of ubiquinol oxidase activity
D239N
mutation in subunit cydA. Mutant is not able to confer the ability to grow aerobically to a strain that has no genomically encoded respiratory oxidases. Heme content similar to wild-type, complete loss of ubiquinol oxidase activity
D29E
mutation in subunit cydB. Mutant is totally inactive, and hemes d and b595 are not present in the isolated enzyme
E107D
mutation in subunit cydA. About 15% of the heme contant of wild-type, complete loss of ubiquinol oxidase activity
E107Q
mutation in transmembrane helix III of subunit cydA. Mutant is totally inactive, but retains its hemes. Residue E107 is protonated at pH 7.6 and is perturbed by the reduction of the heme d/heme b595 binuclear center at the active site
E257A
mutation of an acidic residue of subunit cydA at or near the quinol-binding site, mutation inactivates the enzyme but has no substantial influence on the Fourier transform infrared redox difference spectrum
E99A
mutation in subunit cydA. Mutant is not able to confer the ability to grow aerobically to a strain that has no genomically encoded respiratory oxidases. Complete loss of heme d and heme b595 and of ubiquinol oxidase activity
E99Q
mutation in subunit cydA. Mutant is not able to confer the ability to grow aerobically to a strain that has no genomically encoded respiratory oxidases. Complete loss of heme d and heme b595 and of ubiquinol oxidase activity
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LINKS TO OTHER DATABASES (specific for EC-Number 1.10.3.14)
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