A non-heme iron protein that is involved in the biosynthesis of taurine. Requires catalytic amounts of a cofactor-like compound, such as sulfur, sufide, selenium or methylene blue for maximal activity. 3-Aminopropanethiol (homocysteamine) and 2-mercaptoethanol can also act as substrates, but glutathione, cysteine, and cysteine ethyl- and methyl esters are not good substrates [1,3].