Biology:Aminocyclopropanecarboxylate oxidase
| Aminocyclopropanecarboxylate oxidase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC number | 1.14.17.4 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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In enzymology, an aminocyclopropanecarboxylate oxidase (EC 1.14.17.4) is an enzyme that catalyzes the chemical reaction
- 1-aminocyclopropane-1-carboxylate + ascorbate + O2 [math]\displaystyle{ \rightleftharpoons }[/math] ethylene + cyanide + dehydroascorbate + CO2 + 2 H2O
The 3 substrates of this enzyme are 1-aminocyclopropane-1-carboxylate, ascorbate, and O2, whereas its 5 products are ethylene, cyanide, dehydroascorbate, CO2, and H2O.
This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O2 with reduced ascorbate as one donor, and incorporation of one atom of oxygen into the other donor. The systematic name of this enzyme class is 1-aminocyclopropane-1-carboxylate oxygenase (ethylene-forming). Other names in common use include ACC oxidase, and ethylene-forming enzyme.
Structural studies
As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes 1W9Y and 1WA6.
Reaction Mechanism
Mechanistic and structural studies support binding of ACC and oxygen to an iron center located in the active site of ACC oxidase. The ring-opening of bound ACC is believed to result in the elimination of ethylene together with an unstable intermediate, cyanoformate ion, which then decomposes to cyanide ion and carbon dioxide. Cyanide ion is a known deactivating agent for iron-containing enzymes, but the cyanoformate ion intermediate is believed to play a vital role to carry potentially toxic cyanide away from the active site of ACC oxidase. Cyanoformate was recently identified in condensed media as a tetraphenylphosphonium salt with a weak carbon-carbon bond.
References
- "Expression, purification and characterization of 1-aminocyclopropane-1-carboxylate oxidase from tomato in Escherichia coli". Biochem. J. 307 (Pt 1): 77–85. 1995. doi:10.1042/bj3070077. PMID 7717997.
- "Metal-catalyzed oxidation and mutagenesis studies on the iron(II) binding site of 1-aminocyclopropane-1-carboxylate oxidase". Biochemistry 36 (50): 15999–6007. 1997. doi:10.1021/bi971823c. PMID 9398335.
- Pirrung MC (1999). "Ethylene biosynthesis from 1-aminocyclopropanecarboxylic acid". Acc. Chem. Res. 32 (8): 711–718. doi:10.1021/ar960003.
- "The catalytic mechanism of 1-aminocyclopropane-1-carboxylic acid oxidase". Arch. Biochem. Biophys. 385 (1): 179–85. 2001. doi:10.1006/abbi.2000.2138. PMID 11361015.
- "Steady-state kinetics of substrate binding and iron release in tomato ACC oxidase". Biochemistry 40 (32): 9717–24. 2001. doi:10.1021/bi010329c. PMID 11583172.
- "Purification and properties of the apple fruit ethylene-forming enzyme". Biochemistry 32 (29): 7445–50. July 1993. doi:10.1021/bi00080a015. PMID 8338842.
- "A simple complex on the verge of breakdown: isolation of the elusive cyanoformate ion". Science 344 (6179): 75–8. 2014. doi:10.1126/science.1250808. PMID 24700853. Bibcode: 2014Sci...344...75M. http://urn.fi/URN:NBN:fi:jyu-201511263834.
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