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Literature summary for 2.6.1.13 extracted from
- R180T variant of delta-ornithine aminotransferase associated with gyrate atrophy biochemical, computational, X-ray and NMR studies provide insight into its catalytic features (2019), FEBS J., 286, 2787-2798 .
Cloned(Commentary)
| Cloned (Comment) | Organism |
|---|---|
| recombinant expression of mutant R180T enzyme in CHO-K1 cells | Homo sapiens |
Protein Variants
| Protein Variants | Comment | Organism |
|---|---|---|
| R180T | naturally occuring, gyrate atrophy-causing mutation of ornithine delta-aminotransferase (OAT), the R180T mutation involves an active site residue located at the dimer interface, which in the crystal structure of OAT complexed with 5-fluoromethylornithine engages a salt bridge with the alpha-carboxylate of the substrate analogue. the R180T mutant exhibits a remarkable loss of catalytic activity and is endowed with the ability to catalyse not only the delta-transamination but also, albeit to a lesser extent, the alpha-transamination of L-ornithine. The slight structural changes caused by the R180T mutation, preventing a proper collocation of L-ornithine at the active site of OAT, are responsible for the notable reduction of the catalytic efficiency. Enzyme mutant structure modelling, overview | Homo sapiens |
Inhibitors
| Inhibitors | Comment | Organism | Structure |
|---|---|---|---|
| 5-Fluoromethylornithine | - |
Homo sapiens |  |
KM Value [mM]
| KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| additional information | - |
additional information | steady-state kinetics | Homo sapiens | |
| 2 | 37 | L-ornithine | recombinant mutant R180Tenzyme, pH 8.0, 25°C | Homo sapiens | |
| 3.9 | - |
2-oxoglutarate | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
| 6.5 | - |
L-ornithine | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
| 11.3 | - |
2-oxoglutarate | recombinant mutant R180T enzyme, pH 8.0, 25°C | Homo sapiens | |
Localization
| Localization | Comment | Organism | GeneOntology No. | Textmining |
|---|---|---|---|---|
| mitochondrion | - |
Homo sapiens | 5739 | - |
| additional information | the human enzyme is synthesized on cytoplasmic free ribosomes as a 45 kDa precursor and is processed into a mature protein after mitochondrial entry | Homo sapiens | - |
- |
Natural Substrates/ Products (Substrates)
| Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| L-ornithine + 2-oxoglutarate | Homo sapiens | - |
L-glutamate 5-semialdehyde + L-glutamate | - |
r | |
Organism
| Organism | UniProt | Comment | Textmining |
|---|---|---|---|
| Homo sapiens | P04181 | - |
- |
Posttranslational Modification
| Posttranslational Modification | Comment | Organism |
|---|---|---|
| proteolytic modification | the human enzyme is synthesized on cytoplasmic free ribosomes as a 45 kDa precursor and is processed into a mature protein after mitochondrial entry | Homo sapiens |
Reaction
| Reaction | Comment | Organism | Reaction ID |
|---|---|---|---|
| L-ornithine + a 2-oxo carboxylate = L-glutamate 5-semialdehyde + an L-amino acid | mechanism of the L-ornithine transamination catalysed by ornithine aminotransferase (OAT) and reaction intermediate forms, detailed overview. Like every PLP-dependent transaminases, OAT operates via a ping-pong mechanism, in which two half-reactions complete a full transamination cycle. In the first half-transamination reaction, L-ornithine reacts with the PLP form of the enzyme (OAT-PLP) to yield L-glutamate 5-semialdehyde and the pyridoxamine 5'-phosphate form of the enzyme (OAT-PMP). In the second half transamination, 2-oxoglutarate reacts with OAT-PMP to reform OAT-PLP and L-glutamate | Homo sapiens |
Substrates and Products (Substrate)
| Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
|---|---|---|---|---|---|---|
| L-ornithine + 2-oxoglutarate | - |
Homo sapiens | L-glutamate 5-semialdehyde + L-glutamate | - |
r | |
| additional information | glutamic-gamma-semialdehyde (GSA) product of this reaction undergoes spontaneous cyclization forming DELTA1-pyrroline-5-carboxylate (P5C). NMR analysis of P5C and of 1-pyrroline-2-carboxylate (P2C), generated by alpha-transamination of L-ornithine. Substrate molecular docking study and interaction analysis, NMR analysis, overview | Homo sapiens | ? | - |
- |
|
Subunits
| Subunits | Comment | Organism |
|---|---|---|
| ? | x * 45000, pro-enzyme form, SDS-PAGE | Homo sapiens |
Synonyms
| Synonyms | Comment | Organism |
|---|---|---|
| delta-ornithine aminotransferase | - |
Homo sapiens |
Temperature Optimum [°C]
| Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
|---|---|---|---|
| 25 | - |
assay at | Homo sapiens |
Temperature Stability [°C]
| Temperature Stability Minimum [°C] | Temperature Stability Maximum [°C] | Comment | Organism |
|---|---|---|---|
| 48.8 | - |
Tm of wild-type enzyme in complex with pyridoxamine 5-phosphate | Homo sapiens |
| 60.1 | - |
Tm of enzyme mutant R180T in complex with pyridoxamine 5-phosphate | Homo sapiens |
| 67 | - |
Tm of the free wild-type enzyme | Homo sapiens |
| 72.6 | - |
Tm of enzyme mutant R180T in complex with PLP | Homo sapiens |
Turnover Number [1/s]
| Turnover Number Minimum [1/s] | Turnover Number Maximum [1/s] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| 0.37 | - |
L-ornithine | recombinant mutant R180Tenzyme, pH 8.0, 25°C | Homo sapiens | |
| 0.41 | - |
2-oxoglutarate | recombinant mutant R180T enzyme, pH 8.0, 25°C | Homo sapiens | |
| 34.5 | - |
L-ornithine | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
| 35.7 | - |
2-oxoglutarate | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
pH Optimum
| pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
|---|---|---|---|
| 8 | - |
assay at | Homo sapiens |
Cofactor
| Cofactor | Comment | Organism | Structure |
|---|---|---|---|
| pyridoxal 5'-phosphate | PLP, dependent on | Homo sapiens | |
General Information
| General Information | Comment | Organism |
|---|---|---|
| malfunction | the R180T variant of delta-ornithine aminotransferase is associated with gyrate atrophy. Ornithine delta-aminotransferase deficiency is responsible for gyrate atrophy (GA), an autosomal recessive disorder causing a progressive degeneration of the choroid and retina epithelium leading to blindness in young adults | Homo sapiens |
kcat/KM [mM/s]
| kcat/KM Value [1/mMs-1] | kcat/KM Value Maximum [1/mMs-1] | Substrate | Comment | Organism | Structure |
|---|---|---|---|---|---|
| 0.0016 | - |
L-ornithine | recombinant mutant R180Tenzyme, pH 8.0, 25°C | Homo sapiens | |
| 0.036 | - |
2-oxoglutarate | recombinant mutant R180T enzyme, pH 8.0, 25°C | Homo sapiens | |
| 5.3 | - |
L-ornithine | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
| 6.6 | - |
2-oxoglutarate | recombinant wild-type enzyme, pH 8.0, 25°C | Homo sapiens | |
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