The enzyme protocatechuate decarboxylase (EC 4.1.1.63) catalyzes the chemical reaction

3,4-dihydroxybenzoate ${\displaystyle \rightleftharpoons }$ catechol + CO₂

This enzyme belongs to the family of lyases, specifically the carboxy-lyases, which cleave carbon-carbon bonds. The systematic name of this enzyme class is 3,4-dihydroxybenzoate carboxy-lyase (catechol-forming). Other names in common use include 3,4-dihydroxybenzoate decarboxylase, and protocatechuate carboxy-lyase. This enzyme participates in benzoate degradation via hydroxylation.