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Literature summary for 2.4.2.8 extracted from
- Altering the purine specificity of hypoxanthine-guanine-xanthine phosphoribosyltransferase from Tritrichomonas foetus by structure-based point mutations in the enzyme protein (1998), Biochemistry, 37, 16612-16619.
Application
| Application | Comment | Organism |
|---|---|---|
| medicine | target for anti-trichomonial therapy | Tritrichomonas suis |
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| functional expression of wild-type enzyme and mutants in an enzyme-deficient Escherichia coli strain | Tritrichomonas suis |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| D163E | site directed mutagenesis, slightly changed substrate affinities compared to wild-type | Tritrichomonas suis |
| D163N | site-directed mutagensis, exchange of xanthine binding residue, loss of the binding ability and activity against xanthine and XMP | Tritrichomonas suis |
| F162L | site directed mutagenesis, no effect on purine base specificity | Tritrichomonas suis |
| I104G | site directed mutagenesis, increased Km values for hypoxanthine, guanine, and xanthine | Tritrichomonas suis |
| K134Q | site directed mutagenesis, mutant recognizes adenine as substrate in addition, but less efficient than mutant K134S | Tritrichomonas suis |
| K134S | site directed mutagenesis, mutant recognizes adenine as substrate in addition, increased Km values for hypoxanthine, guanine, and xanthine | Tritrichomonas suis |
| R155E | site directed mutagenesis, reduced affinity to GMP and XMP, catalysation of the forward reaction with guanine and xanthine at accelerated rates, 15fold increased Km for xanthine | Tritrichomonas suis |
| R155K | site directed mutagenesis, reduced affinity to GMP and XMP, catalysation of the forward reaction with guanine and xanthine at accelerated rates, insensitive to phenylglyoxal | Tritrichomonas suis |
| Y156F | site directed mutagenesis, weakened binding of GMP and XMP | Tritrichomonas suis |
| Y156W | site directed mutagenesis, slightly changed substrate affinities compared to wild-type | Tritrichomonas suis |
Inhibitors
| Inhibitors | Comment | Organism | Structure |
|---|---|---|---|
| ADP | - |
Tritrichomonas suis |  |
| AMP | mutant K134S, competitive | Tritrichomonas suis | |
| Phenylglyoxal | irreversible, complete inactivation, alkylation of Arg155, GMP protects, no alkylation of mutant R155K | Tritrichomonas suis | |
KM Value [mM]
| KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| additional information | - |
additional information | wild-type and mutants: Km values for substrates hypoxanthine, guanine, xanthine, IMP, GMP, XMP | Tritrichomonas suis | |
| 0.0346 | - |
adenine | mutant K134S | Tritrichomonas suis | |
| 0.038 | - |
hypoxanthine | mutant K134S | Tritrichomonas suis | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Tritrichomonas suis | - |
- |
- |
Purification (Commentary)
| Purification (Comment) | Organism |
|---|---|
| recombinant wild-type enzyme and mutant/s from Escherichia coli | Tritrichomonas suis |
Reaction
| Reaction | Comment | Organism | Reaction ID |
|---|---|---|---|
| IMP + diphosphate = hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate | catalytic mechanism | Tritrichomonas suis | |
| IMP + diphosphate = hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate | active site structure | Tritrichomonas suis |
Specific Activity [micromol/min/mg]
| Specific Activity Minimum [µmol/min/mg] | Specific Activity Maximum [µmol/min/mg] | Comment | Organism |
|---|---|---|---|
| additional information | - |
kinetics | Tritrichomonas suis |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| adenine + 5-phospho-alpha-D-ribose 1-diphosphate | - |
Tritrichomonas suis | ? | - |
? | |
| guanine + 5-phospho-alpha-D-ribose 1-diphosphate | - |
Tritrichomonas suis | GMP + diphosphate | - |
r | |
| hypoxanthine + 5-phospho-alpha-D-ribose 1-diphosphate | - |
Tritrichomonas suis | IMP + diphosphate | - |
r | |
| additional information | kinetic study | Tritrichomonas suis | ? | - |
? | |
| xanthine + 5-phospho-alpha-D-ribose 1-diphosphate | - |
Tritrichomonas suis | XMP + diphosphate | - |
r | |
Turnover Number [1/s]
| Turnover Number Minimum [1/s] | Turnover Number Maximum [1/s] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| additional information | - |
additional information | wild-type and mutants: kcat for substrates hypoxanthine, guanine, xanthine, IMP, GMP, XMP, diphosphate, 5-phosphoribosyl 1-diphosphate | Tritrichomonas suis |
Ki Value [mM]
| Ki Value [mM] | Ki Value maximum [mM] | Inhibitor | Comment | Organism | Structure |
|---|---|---|---|---|---|
| 0.0254 | - |
ADP | mutant K134S, competitive versus 5-phospho-alpha-D-ribose 1-diphosphate | Tritrichomonas suis | |
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