Involved in the gamma-resorcylate (2,6-dihydroxybenzoate) catabolism (PubMed:15474471). Catalyzes the reversible decarboxylation of gamma-resorcylate to resorcinol (PubMed:15474471). Also catalyzes the decarboxylation of 2,3-dihydroxybenzoate to catechol, but does not act on 2-hydroxybenzoic acid 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, 4-aminobenzoic acid, o-hydroxyphenylacetic acid and vanillic acid (PubMed:15474471). Resorcinol and catechol can both be carboxylated by the reverse reaction (PubMed:15474471). 2,6-dihydroxybenzoate + H(+) = CO2 + resorcinol 2,3-dihydroxybenzoate + H(+) = catechol + CO2 Binds 1 Zn(2+) ion per subunit. Insensitive to oxygen. Decarboxylation and carboxylation are inhibited by AgNO(3) and by diethyl pyrocarbonate, a histidine residue-specific inhibitor. Decarboxylation is also inhibited by HgCl(2) and activated by MgCl(2). Optimum pH is 7.0 for decarboxylation. Optimum temperature is 60 degrees Celsius for decarboxylation. Optimum temperature is 45 degrees Celsius for carboxylation. Aromatic compound metabolism. Homotetramer. Belongs to the metallo-dependent hydrolases superfamily. ACMSD family.