Specific for the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile); converts it to its metabolite 3,5-dibromo-4-hydroxybenzoic acid. a nitrile + 2 H2O = a carboxylate + NH4(+) Homodimer. Introduced by genetic manipulation and expressed in bromoxynil-tolerant cotton by Monsanto (Calgene). Belongs to the carbon-nitrogen hydrolase superfamily. Nitrilase family.