1,4-Dihydroxybenzenoid → Maleylacetate derivative<br><br>Comments:<br>This rule handles the upper hydroquinone pathway, and includes extradiol-type cleavage of hydroquinone derivatives (bt0297), gentisate and homogentisate (bt0174) and 2,6-dihalohydroquinones (bt0069). The initial ring cleavage reaction is catalyzed by an extradiol or an extradiol-type enzyme (<a href="http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=16849108&dopt=AbstractPlus">Vaillancourt et al., 2006</a>) producing a ketone product or an aldehyde intermediate, which is oxidized to form the carboxylate product (bt0003).
