. "The chemical reactions and pathways resulting in the breakdown of protocatechuate, the anion of 3,4-dihydroxybenzoic acid, to yield beta-ketoadipate." . . "protocatechuate catabolic process, ortho-cleavage" . "3,4-dihydroxybenzoate catabolic process, ortho-cleavage" . "protocatechuate breakdown, ortho-cleavage" . "protocatechuate degradation, ortho-cleavage" . .