Catalyzes the deamination of 5-nitroanthranilate (5NAA) to 5-nitrosalicylate (5NSA), the first step in biodegradation of 5-nitroanthranilate. 5-nitroanthranilate + H(+) + H2O = 5-nitrosalicylate + NH4(+) Divalent metal cations. Co(2+), Mn(2+), Zn(2+), Fe(2+) or Ni(2+). Optimum pH is 7.2. Optimum temperature is degrees Celsius. Belongs to the peptidase M20A family.