Involved in the modified meta-cleavage pathway for 2-aminophenol catabolism. The enzyme is also active toward 2-hydroxymuconic 6-semialdehyde, acetaldehyde, propionaldehyde, and butyraldehyde. 2-aminomuconate 6-semialdehyde + H2O + NAD(+) = (2Z,4E)-2-aminomuconate + 2 H(+) + NADH Strongly inhibited by Ag(+) and Hg(+), and comnpletely inhibited by p-chloromercuribenzoic acid. Optimum pH is 7.5. Stable in the range of pH 6.0-8.0. After heating at 40 degrees Celsius, the remaining activity is 40% of the original activity. Homotrimer. Belongs to the aldehyde dehydrogenase family.