Involved in the modified meta-cleavage pathway for the 2-aminophenol catabolism. Only active toward 2-aminomuconic acid. (2Z,4E)-2-aminomuconate + H2O = (3E)-2-oxohex-3-enedioate + NH4(+) Slightly inhibited by Pb(2+), Hg(+) and Cu(2+). Optimum pH is 7.0. Stable in the range of pH 5.5-8.0. Stable up to 55 degrees Celsius. Homotetramer. Belongs to the 2-aminomuconate deaminase family.