The N-terminal domain of the Class III extradiol dioxygenase, Gallate Dioxygenase, which catalyzes the oxidization and subsequent ring-opening of gallate.
Gallate Dioxygenase catalyzes the oxidization and subsequent ring-opening of gallate, an intermediate in the degradation of the aromatic compound, syringate. The reaction product of gallate dioxygenase is 4-oxalomesaconate. The amino acid sequence of the N-terminal and C-terminal regions of gallate dioxygenase exhibits homology with the sequence of PCA 4,5-dioxygenase B (catalytic) and A subunits, respectively. The enzyme is estimated to be a homodimer according to the Escherichia coli enzyme. LigAB-like enzymes are usually composed of two subunits, designated A and B, which form a tetramer composed of two copies of each subunit. In this subfamily, the subunits A and B are fused to make a single polypeptide chain. The dimer interface for this subfamily may resemble the tetramer interface of classical LigAB enzymes. Gallate Dioxygenase belongs to the class III extradiol dioxygenase family, a group of enzymes which use a non-heme Fe(II) to cleave aromatic rings between a hydroxylated carbon and an adjacent non-hydroxylated carbon.