Taurine/alpha-ketoglutarate (alphaKG)-dioxygenase (TauD) is an alphaKG-dependent non-heme Fe(II) containing enzyme from Escherichia coli that plays a critical role in the utilization of taurine as a sulfur source. This enzyme is mechanistically related to a variety of alpha-keto acid-dependent dioxygenases, a large class of enzymes that are essential for the metabolism of a variety of compounds. Despite the prevalence of alphaKG- dependent dioxygenases, little information is available describing the enzyme mechanism of this important enzyme class. TauD is an excellent candidate to serve as a model enzyme for characterizing the general mechanism of alpha-keto acid-dependent dioxygenases because it is small, soluble, and easily purified from a recombinant E. coli strain that overexpresses the tauD gene. I propose to study taurine catabolism by wild-type and variant forms of TauD using a variety of spectroscopic and kinetic methods. Data from these experiments will be integrated with ongoing X-ray crystal structure characterizations, being performed by our collaborators, in order to develop a detailed enzyme mechanism for taurine degradation by TauD. Additional studies will begin to explore the role of genes encoding TauD homologues that were recently discovered in pathogenic bacteria.