Catalyzes the ortho-cleavage of the aromatic ring of hydroxyquinol. benzene-1,2,4-triol + O2 = 2 H(+) + maleylacetate Binds 1 Fe(3+) ion per subunit. Inhibited by 3,5-dichlorocatechol, chlorohydroquinone and 4,5-dibromocatechol. 5-chlorohydroxyquinols and 6-chloro-chlorohydroxyquinols are also substrates. Optimum pH is 7.5. Optimum temperature is 50-55 degrees Celsius. Aromatic compound metabolism; beta-ketoadipate pathway; 3-oxoadipate from 3,4-dihydroxybenzoate: step 2/4. Homodimer. Belongs to the intradiol ring-cleavage dioxygenase family.