Negative regulator of the paaZ and paaABCDEFGHIJK catabolic operons. Binds the consensus sequence 5'-WWTRTGATTCGYGWT-3'. Binding of PaaX is specifically inhibited by phenylacetyl-coenzyme A (PA-CoA). Aromatic compound metabolism; phenylacetate degradation. Belongs to the PaaX family.