Stanford University

Deacetoxycephalosporin-C Synthase (DAOCS) is an oxidoreductase containing a high-spin ferrous resting state coordinated by a 2-His-1-carboxylate facial triad and three water ligands. DAOCS catalyzes ring expansion in penicillin-N using alpha-ketoglutarate (Akg) and O₂ to form deacetoxycephalosporin-C, succinate, CO₂, and H₂O. The mechanism for this reaction has been under scrutiny, and the binding of both the penicillin substrate and Akg cofactor has been under investigation. MCD and Fe EXAFS studies on the resting, penicillin-bound, Akg-bound, and penicillin + Akg-bound forms have provided insight on the active site. These studies show that both the penicillin and Akg are capable of binding to the active site, but a different site is formed when both the penicillin and Akg are present. This information can provide insight on the mechanism of the reaction.