The A subunit of Uncharacterized proteins with similarity to Protocatechuate 4,5-dioxygenase (LigAB)
The proteins of unknown function in this subfamily are similar to the A subunit of the Protocatechuate (PCA) 4,5-dioxygenase (LigAB). LigAB belongs to the class III extradiol dioxygenase family, composed of enzymes which use a non-heme Fe(II) to cleave aromatic rings between a hydroxylated carbon and an adjacent non-hydroxylated carbon. Dioxygenases play key roles in the degradation of aromatic compounds. PCA 4,5-dioxygenase catalyzes the oxidization and subsequent ring-opening of PCA (or 3,4-dihydroxybenzoic acid), which is an intermediate in the breakdown of lignin and other compounds.