Reaction: methylarsonous acid + NADPH + O2 = methylarsonate + NADP+ + H2O
Glossary: roxarsone (III) = (4-hydroxy-3-nitrophenyl)arsonous acid
methylarsonous acid = methylarsonite
Other name(s): arsH (gene name)
Systematic name: trivalent organoarsenical,NADPH:oxygen oxidoreductase (pentavalent organoarsenical-forming)
Comments: Contains FMN. The enzyme, found in bacteria, detoxifies trivalent methylated and aromatic arsenicals such as methylarsonous acid, phenylarsonous acid and roxarsone (III) by oxidation to pentavalent species. Methylarsonous acid can be formed from the herbicide methylarsonate by EC 1.20.4.2, methylarsonate reductase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Chen, J., Bhattacharjee, H. and Rosen, B.P. ArsH is an organoarsenical oxidase that confers resistance to trivalent forms of the herbicide monosodium methylarsenate and the poultry growth promoter roxarsone. Mol. Microbiol. 96 (2015) 1042-1052. [PMID: 25732202]
2. Paez-Espino, A.D., Nikel, P.I., Chavarria, M. and de Lorenzo, V. ArsH protects Pseudomonas putida from oxidative damage caused by exposure to arsenic. Environ. Microbiol. 22 (2020) 2230-2242. [PMID: 32202357]
3. Sedlacek, V., Kryl, M. and Kucera, I. The ArsH protein product of the Paracoccus denitrificans ars operon has an activity of organoarsenic reductase and is regulated by a redox-responsive repressor. Antioxidants (Basel) 11 (2022) 902. [PMID: 35624766]
4. Kucera, I. and Sedlacek, V. Flavin-dependent enzymatic and photochemical interconversions between phenylarsonic and phenylarsonous acids. Biometals 38 (2025) 903-915. [PMID: 40240666]