Catalysis of the reaction: 2-amino-3-carboxymuconate 6-semialdehyde + H+ = 2-aminomuconate 6-semialdehyde + CO2.
2-amino-3-(3-oxoprop-1-en-1-yl)but-2-enedioate carboxy-lyase (2-aminomuconate-semialdehyde-forming)