Transforms 5-carboxymethyl-2-hydroxy-muconic semialdehyde (CHMS) into 5-carboxymethyl-2-hydroxy-muconic acid (CHM). Aromatic compound metabolism; 4-hydroxyphenylacetate degradation; pyruvate and succinate semialdehyde from 4-hydroxyphenylacetate: step 3/7. Belongs to the aldehyde dehydrogenase family.