Protein Variants | Comment | Organism |
---|---|---|
A143P | site-directed mutagenesis of the delta-site of substrate oxidation, the electronic absorption spectra and dissociation constants for binding of cyanide and azide to the isolated heme are not significantly different for the mutant compared to wild-type, also the rate constants in the peroxidase reaction mechanism are not significantly affected by the replacement of A134 by proline. The insertion of a proline does not substantially alter the product distribution in APX | Pisum sativum |
additional information | attempts to decrease heme accessibility through introduction of a Phe residue at position134 are unsuccessful because the A134F variant is isolated as the apoform from Escherichia coli and reconstitution protocols with exogenous heme do not generate catalytically active enzyme | Pisum sativum |
Inhibitors | Comment | Organism | Structure |
---|---|---|---|
phenylhydrazine | a suicide substrate | Pisum sativum |
KM Value [mM] | KM Value Maximum [mM] | Substrate | Comment | Organism | Structure |
---|---|---|---|---|---|
additional information | - |
additional information | pre-steady state and steady-state kinetic analysis of wild-type and mutant enzymes, formation of high-valent Compound I and Compound II intermediates, detailed overview. The steady-state oxidation of ascorbate by APX does not obey simple Michaelis-Menten kinetics, and a sigmoidal dependence of rate on substrate concentration is observed. The mutant A134P variant behaves similarly. In contrast, oxidation of guaiacol by A134P exhibits conventional Michaelis-Menten type kinetics | Pisum sativum |
Localization | Comment | Organism | GeneOntology No. | Textmining |
---|---|---|---|---|
cytosol | - |
Pisum sativum | 5829 | - |
Metals/Ions | Comment | Organism | Structure |
---|---|---|---|
Fe2+ | in the heme group | Pisum sativum |
Natural Substrates | Organism | Comment (Nat. Sub.) | Natural Products | Comment (Nat. Pro.) | Rev. | Reac. |
---|---|---|---|---|---|---|
2 L-ascorbate + H2O2 + 2 H+ | Pisum sativum | - |
L-ascorbate + L-dehydroascorbate + 2 H2O | - |
? |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Pisum sativum | P48534 | - |
- |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
2 L-ascorbate + H2O2 + 2 H+ | - |
Pisum sativum | L-ascorbate + L-dehydroascorbate + 2 H2O | - |
? | |
guaiacol + H2O2 | - |
Pisum sativum | ? | - |
? | |
additional information | there are two main sites for substrate oxidation. The first, close to the gamma-heme edge, is used by ascorbate peroxidase and is presumed to be the main physiological binding site. The second site is close to the delta-heme edge. Role of Ala134 in controlling peroxidase reactivity at the delta-heme edge, overview. Assaying with L-ascorbate, guaiacol and 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonic acid | Pisum sativum | ? | - |
- |
Synonyms | Comment | Organism |
---|---|---|
APX | - |
Pisum sativum |
APX1 | - |
Pisum sativum |
ascorbate peroxidase | - |
Pisum sativum |
Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
---|---|---|---|
25 | - |
assay at | Pisum sativum |
pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
---|---|---|---|
7 | - |
assay at | Pisum sativum |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
heme | ascorbate peroxidase binds some substrates at the gamma-heme edge | Pisum sativum |
General Information | Comment | Organism |
---|---|---|
evolution | ascorbate peroxidase (APX) is a class I heme peroxidase. Heme peroxidases catalyse the H2O2-dependent oxidation of a wide variety of substrates. The family of heme peroxidases share a common mechanism of oxidation which involves the formation of high-valent Compound I and Compound II intermediates. Ascorbate peroxidase and manganese peroxidase bind some substrates at the gamma-heme edge, others at the delta-heme edge | Pisum sativum |