Abstract

2-Oxoglutarate (2OG) dependent non-heme mononuclear iron (NHM-Fe) enzymes catalyze a large array of chemical transformations, ranging from hydroxylation and dealkylation, to desaturation, epoxidation, halogenation, epimerization, endoperoxidation, as well as ring expansion/contraction reactions. In recent years, detailed mechanistic studies on this family of enzymes have revealed an emerging paradigm to explain their catalytic diversity: (1) the electronic structures of the reactive iron intermediates; (2) the presence of polar or redox-active residues in the secondary coordination sphere of the iron; and/or (3) the electronic properties of the enzyme substrates. To futher explore the interplay among these factors in directing reaction outcomes, we have carried out kinetic and spectroscopic studies on multiple 2OG NHM-Fe enzymes that are involved the biosynthesis of various natural products having antibiotic and antimicrobial activity. In this talk, I will present our recent results on elucidating the reaction mechanisms of two newly discovered 2OG NHM-Fe enzymes through the detection and the characterization of reactive intermediates during enzyme catalysis under pre-steady state conditions. The enzymes are FtmOx1 from Aspergillus fumigatus, which catalyzes a unique endoperoxide bond formation in the biosynthesis of a mycotoxin, verruculogen; and AsqJ from Aspergillus nidulans, which catalyzes a stepwise oxidation (desaturation and epoxidation) in the biosynthesis of a quinolone-type fungal alkaloid, 4’-methoxy-viridicatin.