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Literature summary for 1.8.3.2 extracted from

  • Israel, B.A.; Kodali, V.K.; Thorpe, C.
    Going through the barrier coupled disulfide exchange reactions promote efficient catalysis in quiescin sulfhydryl oxidase (2014), J. Biol. Chem., 289, 5274-5284 .
    View publication on PubMedView publication on EuropePMC
Search for more literature for 1.8.3.2

Crystallization (Commentary)

Crystallization (Comment) Organism
TbQSOX crystal structure analysis, PDB ID 3QD9 Trypanosoma brucei

Protein Variants

Protein Variants Comment Organism
additional information the wild-type CGAC motif in the thioredoxin domain of enzyme TbQSOX is replaced by the more oxidizing CPHC or more reducing CGPC sequence, resulting in mutants CIPHCII and CIGPCII. Construction of a truncated mutant containing only the thioredoxin domain TbQSOX-TRX, corresponding to residues 20-199 Trypanosoma brucei

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
 additional information stopped-flow kinetic measurements Trypanosoma brucei
0.03
-
 dithiothreitol mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
0.04
-
 RNAse A mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
0.17
-
 dithiothreitol wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei
0.22
-
 dithiothreitol mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
0.32
-
 RNAse A mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
0.36
-
 RNAse A wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
RNase A + O2 Trypanosoma brucei
-
 RNase A disulfide + H2O2
-
 ?

Organism

Organism UniProt Comment Textmining
Trypanosoma brucei
-
-
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
dithiothreitol + O2
-
 Trypanosoma brucei dithiothreitol disulfide + H2O2
-
 r
glutathione + O2
-
 Trypanosoma brucei glutathione disulfide + H2O2
-
 r
additional information redox potentials of TbQSOX-bound FAD and of the CIIIXXCIV proximal disulfide, overview. Determining the redox potential of the CIXXCII motif requires isolating the redox-active TRX domain from the HRR-ERV domains to prevent transfer of reducing equivalents from the CIXXCII dithiol to the CIIIXXCIV and FAD centers of TbQSOX, overview Trypanosoma brucei ?
-
 ?
RNase A + O2
-
 Trypanosoma brucei RNase A disulfide + H2O2
-
 ?

Subunits

Subunits Comment Organism
More domain organization of TbQSOX together with key catalytic steps deduced from studies of both metazoan and protist QSOXs, overview Trypanosoma brucei

Synonyms

Synonyms Comment Organism
QSOX
-
 Trypanosoma brucei
quiescin sulfhydryl oxidase
-
 Trypanosoma brucei

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
25
-
 assay at Trypanosoma brucei

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
0.79
-
 RNAse A mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
0.9
-
 dithiothreitol mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
11
-
 RNAse A mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
13.7
-
 dithiothreitol mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
21.9
-
 RNAse A wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei
45.1
-
 dithiothreitol wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7
-
 assay at Trypanosoma brucei

Cofactor

Cofactor Comment Organism Structure
FAD reduction of the oxidizing FAD cofactor is followed by the strongly favorable reduction of molecular oxygen, mixed disulfide bond formation is accompanied by the generation of a charge transfer complex with the flavin cofactor. Generation of a 5-deaza-FAD-substituted enzyme by reconstituting the apoprotein with the flavin analogue. Redox potentials of TbQSOX-bound FAD and of the CIIIXXCIV proximal disulfide, overview Trypanosoma brucei

General Information

General Information Comment Organism
evolution mechanistic parallels between the eukaryotic QSOX enzymes and the DsbA/B system catalyzing disulfide bond generation in the bacterial periplasm are detected suggesting that the strategy of linked disulfide exchanges may be exploited in other catalysts of oxidative protein folding Trypanosoma brucei
additional information in the redox center, CXXC motif of the thioredoxin domain is comparatively oxidizing, consistent with an ability to transfer disulfide bonds to a broad range of thiol substrates. In contrast, the proximal CXXC disulfide in the ERV (essential for respiration and vegetative growth) domain of TbQSOX is strongly reducing, representing a major apparent thermodynamic barrier to overall catalysis. Reduction of the oxidizing FAD cofactor is followed by the strongly favorable reduction of molecular oxygen, role of a mixed disulfide intermediate between thioredoxin and ERV domains, overview. Mixed disulfide bond formation is accompanied by the generation of a charge transfer complex with the flavin cofactor providing thermodynamic coupling among the three redox centers of QSOX and avoids the strongly uphill mismatch between the formal potentials of the thioredoxin and ERV disulfides. Domain organization of TbQSOX together with key catalytic steps deduced from studies of both metazoan and protist QSOXs, overview Trypanosoma brucei

kcat/KM [mM/s]

kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
19.75
-
 RNAse A mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
30
-
 dithiothreitol mutant CIPHCII, pH 7.0, 25°C Trypanosoma brucei
34.4
-
 RNAse A mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
60.8
-
 RNAse A wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei
62.3
-
 dithiothreitol mutant CIGPCII, pH 7.0, 25°C Trypanosoma brucei
265.3
-
 dithiothreitol wild-type enzyme, pH 7.0, 25°C Trypanosoma brucei