4,5-dihydroxyphthalate + H(+) = 3,4-dihydroxybenzoate + CO2 Xenobiotic degradation; phthalate degradation; 3,4-dihydroxybenzoate from phthalate: step 3/3. Induced by phthalate and repressed by glucose. To P.testosteroni DHP decarboxylase.