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Literature summary for 1.8.1.B1 extracted from

  • Huang, H.H.; Arscott, L.D.; Ballou, D.P.; Williams, C.H.
    Acid-base catalysis in the mechanism of thioredoxin reductase from Drosophila melanogaster (2008), Biochemistry, 47, 1721-1731.
    View publication on PubMed

Protein Variants

Protein Variants Comment Organism
H464Q mutant enzyme has only 2% of the wild-type activity. The pH dependence of Vmax for wild-type DmTrxR has pKa values of 6.4 and 9.3 on the DmTrxR-DmTrx-2 complex, whereas H464Q DmTrxR only has an observable pKa at 6.4, indicating that the pKa at pH 9.3 is contributed mainly by His464. The pKa at pH 6.4 is assigned to Cys57 and Cys490. The thiolate on Cys490 is the nucleophile in the reduction of Trx. In contrast to wild-type DmTrxR, H464Q DmTrxR does not stabilize a thiolate-FAD charge-transfer complex in the presence of excess NADPH. The rates of steps in both the reductive and the oxidative half-reactions are markedly diminished in H464Q DmTrxR as compared to those of wild-type enzyme, indicating that His464 is involved in both half-reactions Drosophila melanogaster

Organism

Organism UniProt Comment Textmining
Drosophila melanogaster
-
-
-

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
GSSG + NADPH + H+
-
Drosophila melanogaster GSH + NADP+
-
?
thioredoxin disulfide + NADPH + H+
-
Drosophila melanogaster thioredoxin + NADP+
-
?

Synonyms

Synonyms Comment Organism
DmTrxR
-
Drosophila melanogaster

Cofactor

Cofactor Comment Organism Structure
FAD each catalytically active unit consists of three redox centers: FAD and an N-terminal Cys57/Cys62 redox-active disulfide from one monomer and a Cys489/Cys490 C-terminal redox-active disulfide from the second monomer Drosophila melanogaster