Cloned (Comment) | Organism |
---|---|
gene IDO1, recombinant expression of His-tagged enzyme in Escherichia coli strain BL21 Star (DE3), real-time PCR enzyme expression analysis | Homo sapiens |
Inhibitors | Comment | Organism | Structure |
---|---|---|---|
1-methyl-L-tryptophan | competitive versus L-Trp and noncompetitive versus O2. When 1-Me-L-Trp is the only indoleamine in the reaction mixture, it is a very slow substrate for hIDO1 | Homo sapiens | |
norharmane | NHM, noncompetitive versus L-Trp and competitive versus O2 | Homo sapiens |
KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
---|---|---|---|---|---|
additional information | - |
additional information | stopped-flow and Michaelis-Menten steady-state kinetic measurements, kinetic model for catalytic dioxygenation of L-Trp by hIDO1, detailed overview. At low O2, the reversibility of the first step is essential for accurate reproduction of experimental O2 kcat/KM ratios | Homo sapiens |
Metals/Ions | Comment | Organism | Structure |
---|---|---|---|
Fe2+ | ferric heme | Homo sapiens |
Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
---|---|---|---|---|---|---|
D-tryptophan + O2 | Homo sapiens | - |
N-formyl-D-kynurenine | - |
? | |
L-tryptophan + O2 | Homo sapiens | - |
N-formyl-L-kynurenine | - |
? |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Homo sapiens | P14902 | - |
- |
Purification (Comment) | Organism |
---|---|
recombinant His-tagged enzyme from Escherichia coli strain BL21 Star (DE3) by two steps of nickel affinity chromatography and dialysis | Homo sapiens |
Reaction | Comment | Organism | Reaction ID |
---|---|---|---|
L-tryptophan + O2 = N-formyl-L-kynurenine | steady-state kinetic catalytic mechanism of hIDO1 | Homo sapiens |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
D-tryptophan + O2 | - |
Homo sapiens | N-formyl-D-kynurenine | - |
? | |
L-tryptophan + O2 | - |
Homo sapiens | N-formyl-L-kynurenine | - |
? | |
additional information | using a cytochrome b5-based activating system, the initial rates of O2 decay with a Clark-type oxygen electrode at physiologically-relevant levels of both substrates are measured. Kinetics are also studied in the presence of two inhibitory substrate analogues: 1-methyl L-tryptophan and norharmane. Quantitative analysis supports a steady-state rather than a rapid equilibrium kinetic mechanism, where the rates of individual pathways, leading to a ternary complex, are significantly different, and the overall rate of catalysis depends on contributions of both routes. One path, where O2 binds to ferrous hIDO1 first, is faster than the second route, which starts with the binding of L-Trp. L-Trp complexation with free ferrous hIDO1 is more rapid than that of O2. As the level of L-Trp increases, the slower route becomes a significant contributor to the overall rate, resulting in observed substrate inhibition. When 1-Me-L-Trp is the only indoleamine in the reaction mixture, it is a very slow substrate for hIDO1 | Homo sapiens | ? | - |
? |
Synonyms | Comment | Organism |
---|---|---|
hIDO1 | - |
Homo sapiens |
Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
---|---|---|---|
25 | - |
assay at | Homo sapiens |
pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
---|---|---|---|
7 | - |
assay at | Homo sapiens |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
heme | ferric heme | Homo sapiens |
Ki Value [mM] | Ki Value maximum [mM] | Inhibitor | Comment | Organism | Structure |
---|---|---|---|---|---|
0.0052 | - |
1-methyl-L-tryptophan | pH 7.0, 25°C, versus L-tryptophan and O2 | Homo sapiens | |
0.012 | - |
norharmane | pH 7.0, 25°C, versus O2 | Homo sapiens | |
0.03 | - |
norharmane | pH 7.0, 25°C, versus L-tryptophan | Homo sapiens |
Organism | Comment | Expression |
---|---|---|
Homo sapiens | the enzyme is cytokine-inducible | up |
General Information | Comment | Organism |
---|---|---|
physiological function | the cytokine-inducible extrahepatic human indoleamine 2,3-dioxygenase (hIDO1) catalyzes the first step of the kynurenine pathway. Immunosuppressive activity of hIDO1 in tumor cells weakens host T-cell immunity, contributing to the progression of cancer | Homo sapiens |