In mammals, sulfur metabolism is mainly controlled by the action of two enzymes: cysteine dioxygenase (CDO) and cystamine dioxygenase (ADO). The activity of these enzymes is important in controlling metabolic cysteine and taurine concentrations and is associated with autoimmune and neurological conditions, cellular sensing and signaling, energy balance, and fat metabolism. CDO contains a self-processed cofactor, and both enzymes utilize a mononuclear ferrous center to facilitate the incorporation of molecular oxygen into the thiol moiety of their respective substrates.