Faculty

Redox enzymes participate in all aerobic organisms and are crucial to normal metabolism of endogenous substrates, as well as pharmacological and toxic substances. We are examining flavoprotein, hemoprotein, and nonheme iron oxygenases, and other redox proteins that can be isolated in homogeneous form. We study how several of these enzymes activate oxygen and control reactions with organic compounds. Our investigations use a variety of approaches, including spectral and rapid reaction techniques for characterizing active sites and intermediates in the reactions, site-directed mutagenesis to specifically test roles of particular amino acid residues in each of the steps of the reaction, and X-ray crystallography, in collaboration with other laboratories to define the relationship of structure and function in these enzymes and their mutants.

1. Flavoprotein oxygenases carry out hydroxylations of aromatic compounds. Some of these enzymes use both a flavin reductase and an oxygenase, and others use a single protein. We are studying how the protein environments efficiently effect these hydroxylation, which have never been accomplished by organic models. Dr. Barrie Entsch, formerly at the University of New England, Australia, helps direct this project.

2. Nonheme iron-containing dioxygenases and monooxygenases in soil bacteria are critical to the microbial degradation of persistent and toxic aromatic and aliphatic compounds in the environment. We are investigating electron transfer reactions between the FMN and [2Fe–2S] centers and the mechanism of the oxygenation reaction at the mononuclear iron center of the 2-component phthalate dioxygenase system, which is a prototype for Rieske nonheme iron oxygenases that catalyze oxygenations of poorly reactive aromatic compounds.

3. Dr. Charles Williams in our laboratory heads up the study of thioredoxin reductase and related flavoprotein dithiol reductases in collaboration with laboratories in Germany and Scotland. We are investigating enzymes from human, mosquito, and the malarial causative agent P. falciparum with the hope of developing inhibitory drugs for combatting malaria.

4. We are collaborating with several laboratories on studies of additional redox enzymes. Among these are: Paul Hollenberg (U of Michigan) and John Dawson (South Carolina) on P450 enzymes, Rowena Matthews (U of Michigan) on methionine synthase and tetrahydrofolate reductase, and Neil Marsh (U of Michigan) on glutamate mutase.

Awards

Fellow of the American Association for the Advancement of Science

Representative Publications

1. Valton, J., Mathevon, C., Fontecave, M., Niviere, V., Ballou, D.P., "The Two-component FMN-Dependent Monooxygenase ActVA-ActVB from Streptomyces coelicolor: Mechanism and Regulation", J. Biol. Chem, (in press).

2. Padovani, D., Labunska, T., Palfey, B.A., Ballou, D.P., Banerjee, R., "Adenosyltransferase tailors and delivers coenzymes B₁₂", Nature Chem. Biol., 2008, 4, 194.

3. Huang, H-H., Arscott, L.D., Ballou, D.P., Williams, C.H. Jr., "Acid-base catalysis in the mechanism of thioredozin reductase from Drosophila melanogaster", Biochemistry, 2008, (Epub ahead of print).

4. Alexander J.P., Ryan, T.J., Ballou, D.P, Coward, J.K., "Gamma Glutamyl Hydrolase: Kinetic Characterization of Isopeptide Hydrolysis Using Fluorogenic Substrates", Biochemistry, 2008, 47, 1228.

5. Tarasev, M., Kaddis, C.S., Yin, S., Loo, J.A., Burgner, J., Ballou, D.P., "Hezameric Arrangement of Subunits in Phthalate Dioxygenase" Arch. Biochem. Biophys., 2007, 466, 31.

6. Sucharitakul, J., Phongsak, T., Entsch, B., Svasti, J., Chaiyen, P., Ballou, D.P., "Kinetics of a Two-Component p-Hydroxyphenylacetate Hydroxylase Explain How Reduced Flavin Is Transferred from the Reductase to the Oxygenase" Biochemisty, 2007, 46, 8611.

7. Tapley, T.L., Eichner, T., Gleiter, S., Ballou, D.P., Bardwell, J.C., "Kinetic Characterization of the Disulfide Bond Forming Enzyme DsbB" J. Biol. Chem., 2007, 282, 10263.