Persulfide dioxygenase (PDO, also known as sulfur dioxygenase, SDO, ) is a non-heme iron-dependent oxygenase that catalyses the oxidation of glutathione persulfide (GSSH) to glutathione (GSH) and persulfite and play important and varied roles in all kingdoms, including sulfide detoxification []. These enzymes belong to the metallo-beta-lactamase (MBL) superfamily as they consist of the same structural fold of two β-sheets surrounded by α-helices, which supports the metal-binding feature. The PDOs share high sequence and structural similarity with glyoxalases II (classical di-zinc MBL hydrolase), specially at the metal-binding centre. PDOs have a Fe2 binding site and a secondary coordination sphere-based hydrogen bond network that is absent in glyoxalases II, in which the corresponding residues are involved in coordinating a second metal ion. This suggests that PDOs may evolve from a hydrolytic enzyme with two coordinated ions []. Based on sequence analysis, three subclasses of PDO were described: ETHE1, which is present in animals, plants, and bacteria (in the latter they are also called type 1 PDOs), persulfide dioxygenase A (PDOA, or type 2 PDOs), also known as sulfur dioxygenase A (SdoA), which is common in Proteobacteria, and Blh, which is an acronym for beta-lactamase-like hydrolase []. In humans, mutations in PDO ETHE1 cause a rare autosomal recessive metabolic disorder called ethylmalonic encephalopathy []. In Arabidopsis thaliana, ETHE1 is essential for embryo and endosperm development [].This entry represents the MBL-fold metallo-hydrolase domain.
