Research Interests   Oxygenase mechanisms, metalloproteins, magnetic resonance techniques, kinetics.

We investigate the mechanisms of oxygenases, the enzymes nature uses to catalyze the incorporation of oxygen into biological molecules. Oxygen incorporation reactions are important for a wide variety of reasons, ranging from activation of steroid hormones in humans to the detoxification of compounds in the environment. The oxygenases we study contain a metal which is the key to the chemistry they catalyze. Enzyme mechanisms involve both the chemical reactions occurring at the active site and the regulation of the reaction imposed by the complex protein structure. Consequently, we use many types of biochemical and physical techniques including transient kinetics, site directed mutagenesis, diagnostic substrate reactions, and EPR spectroscopy. This is extended to X-ray crystallography and other spectroscopies through collaborations.

Currently, we are studying two large families of oxygenases. The first is typified by methane monooxygenases, the enzyme primarily responsible for preventing the vast amounts of biologically generated methane from reaching the atmosphere. This enzyme splits O₂ and incorporates one atom of oxygen into methane to form methanol, while reducing the second atom to water. The second oxygenase family includes several dioxygenase enzymes that also split O₂ but incorporate both atoms into biomolecules. These enzymes are the major means by which the enormous quantities of aromatic compounds that enter the environment annually are reassimilated into the carbon cycle. Related collaborative projects include studies of the biosynthesis of penicillin, fosfomycin, and ethylene (a plant hormone).

Brazeau, B. J. and Lipscomb J. D. "Key Amino Acid Residues in the Regulation of Soluble Methane Monooxygenase Catalysis by Component B" Biochemistry, 42, 5618-5631, (2003). (pubmed)

Yang, T.-C., Wolfe, M. D., Neibergall, M. B., Mekmouche, Y., Lipscomb, J. D., and Hoffman, B. M. “Substrate Binding to NO-Ferro-Naphthalene 1,2-Dioxygenase Studied by High-Resolution Q-Band Pulsed 2H-ENDOR Spectroscopy" J. Am. Chem. Soc., 125, 7056-7066 (2003). (pubmed)

Rocklin, A. M., Kato, K., Liu, H.-w., Que, L., Jr., and Lipscomb, J. D. “Mechanistic Studies of 1-Aminocyclopropane-1-Carboxylic Acid Oxidase: Single Turnover Reaction”, J. Biol. Inorg. Chem., 9, 171-182 (2004). (pubmed)

Vetting, M. W., Wackett, L. P., Que, L., Jr., Lipscomb, J. D., and Ohlendorf, D. H. “A Crystallographic Comparison of Manganese and Iron Dependent Homoprotocatechuate 2,3-Dioxygenases” J. Bact., 186, 1945-1958 (2004). (pubmed)

Groce, S. L., Miller-Rodeberg, M. A., and Lipscomb, J. D. “Single Turnover Kinetics of Homoprotocatechuate 2,3-Dioxygenase” Biochemistry 43, 15141-15153 (2004). (pubmed)

Groce, S. L., and Lipscomb, J. D. “Aromatic Ring Cleavage by Homoprotocatechuate 2,3-Dioxygenase: Role of His 200 in the Kinetics of Interconversion of Reaction Cycle Intermediates”, Biochemistry 44, 7175-7188 (2005). (pubmed)

Valley, M. P., Brown, C. K., Burk, D. L., Vetting, M. W., Ohlendorf, D. H., and Lipscomb, J. D. “Roles of the Equatorial Tyrosyl Iron Ligand of Protocatechuate 3,4-Dioxygenase in Catalysis” Biochemistry, 44, 11024-11039 (2005). (pubmed)

Zhang, J., and Lipscomb, J. D. “Role of the C-terminal Region of the B Component of Methylosinus trichosporium OB3b methane monooxygenase in the regulation of oxygen activation” Biochemistry, 45, 1459-1469 (2006). (pubmed)

Zheng, H., and Lipscomb, J. D. “Regulation of methane monooxygenase catalysis based on size exclusion and quantum tunneling” Biochemistry, 45, 1689-1692 (2006). (pubmed)

Zhang, J., Wallar, B. J., Popescu, C. V., Renner, D. B., Thomas, D. D., and Lipscomb, J. D. “Methane Monooxygenase Hydroxylase and B Component Interactions” Biochemistry, 45, 2913-2926 (2006). (pubmed).