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Literature summary for 1.8.3.2 extracted from

  • Kodali, V.K.; Thorpe, C.
    Quiescin sulfhydryl oxidase from Trypanosoma brucei: catalytic activity and mechanism of a QSOX family member with a single thioredoxin domain (2010), Biochemistry, 49, 2075-2085.
    View publication on PubMedView publication on EuropePMC

Cloned(Commentary)

Cloned (Comment) Organism
expression in Escherichia coli Trypanosoma brucei

Protein Variants

Protein Variants Comment Organism
C69S about 5% of wild-type activity with substrate dithiothreitol, 0.5% with substrate rRNase Trypanosoma brucei
C72S about 5% of wild-type activity with substrate dithiothreitol, 0.5% with substrate rRNase Trypanosoma brucei
additional information replacement of either cysteine of the proximal disulfide, i.e. CIII or CIV with serine essentially abolishes activity both towards dithiothreitol and rRNase. Mutations of the terminal CxxC disulfide do not show significant loss of activity towards dithiothreitol or rRNase, the visible spectra of both CVS and CVIS mutants are comparable to that of the wild-type protein Trypanosoma brucei

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
0.086
-
dithiothreitol pH 7.5, 37°C Trypanosoma brucei
0.36
-
rRNaseA pH 7.5, 37°C Trypanosoma brucei

Localization

Localization Comment Organism GeneOntology No. Textmining
membrane type I membrane protein Trypanosoma brucei 16020
-

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
54000
-
PAGE Trypanosoma brucei
54300
-
analytical ultracentrifugation Trypanosoma brucei

Organism

Organism UniProt Comment Textmining
Trypanosoma brucei Q585M6
-
-

Storage Stability

Storage Stability Organism
-20°C, 50 mM potassium phosphate buffer containing 1 mM EDTA, pH 7.5, stable for at least 1 year Trypanosoma brucei
4°C, 50 mM potassium phosphate buffer containing 1 mM EDTA, pH 7.5, stable for at least 6 months Trypanosoma brucei

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2 dithiothreitol + O2
-
Trypanosoma brucei dithiothreitol disulfide + H2O2
-
?
2 glutathione + O2
-
Trypanosoma brucei glutathione disulfide + H2O2
-
?
additional information unfolded reduced proteins are more than 200fold more effective substrates on a per-thiol basis than glutathione, and some 10fold better than the parasite bis-glutathione analog, trypanothione. The CxxC motif in the single Trx domain is crucial for efficient catalysis of the oxidation of both reduced RNase and the model substrate dithiothreitol. The proximal disulfide CIII-CIV, which interacts with the flavin, is catalytically crucial. Turnover is limited by an internal redox step leading to 2-electron reduction of the FAD cofactor Trypanosoma brucei ?
-
?
rRNaseA + O2
-
Trypanosoma brucei ? + H2O2
-
?

Subunits

Subunits Comment Organism
monomer 1 * 54000, SDS-PAGE Trypanosoma brucei

Synonyms

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

Turnover Number [1/s]

Turnover Number Minimum [1/s] Turnover Number Maximum [1/s] Substrate Comment Organism Structure
22
-
rRNaseA pH 7.5, 37°C Trypanosoma brucei
45
-
dithiothreitol pH 7.5, 37°C Trypanosoma brucei

pH Optimum

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

Cofactor

Cofactor Comment Organism Structure
FAD turnover is limited by an internal redox step leading to 2-electron reduction of the FAD cofactor Trypanosoma brucei

kcat/KM [mM/s]

kcat/KM Value [1/mMs-1] kcat/KM Value Maximum [1/mMs-1] Substrate Comment Organism Structure
2.3
-
glutathione pH 7.5, 37°C Trypanosoma brucei
180
-
rRNaseA pH 7.5, 37°C Trypanosoma brucei
230
-
dithiothreitol pH 7.5, 37°C Trypanosoma brucei