Reaction: (Z)-phenylacetaldehyde oxime = phenylacetonitrile + H2O
For diagram of reaction, click here
Other name(s): PAOx dehydratase; arylacetaldoxime dehydratase; OxdB; (Z)-phenylacetaldehyde-oxime hydro-lyase
Systematic name: (Z)-phenylacetaldehyde-oxime hydro-lyase (phenylacetonitrile-forming)
Comments: The enzyme from Bacillus sp. OxB-1 contains protoheme IX, the iron of which must be in the form iron(II) for activity. (Z)-Phenylacetaldoxime binds to ferric heme (the iron(III) form) via the oxygen atom whereas it binds to the active ferrous form via the nitrogen atom. In this way, the oxidation state of the heme controls the coordination stucture of the substrate—heme complex, which regulates enzyme activity [2]. The enzyme is active towards several (Z)-arylacetaldoximes and (E/Z)-alkylaldoximes as well as towards arylalkylaldoximes such as 3-phenylpropionaldoxime and 4-phenylbutyraldoxime. However, it is inactive with phenylacetaldoximes that have a substituent group at an α-site of an oxime group, for example, with (E/Z)-2-phenylpropionaldoxime and (E/Z)-mandelaldoxime. The activity of the enzyme is inhibited completely by the heavy-metal cations Cu+, Cu2+, Ag+ and Hg+ whereas Fe2+ and Sn2+ have an activatory effect.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Kato, Y., Nakamura, K., Sakiyama, H., Mayhew, S.G. and Asano, Y. Novel heme-containing lyase, phenylacetaldoxime dehydratase from Bacillus sp. strain OxB-1: purification, characterization, and molecular cloning of the gene. Biochemistry 39 (2000) 800-809. [PMID: 10651646]
2. Kobayashi, K., Yoshioka, S., Kato, Y., Asano, Y. and Aono, S. Regulation of aldoxime dehydratase activity by redox-dependent change in the coordination structure of the aldoxime-heme complex. J. Biol. Chem. 280 (2005) 5486-5490. [PMID: 15596434]