Research Abstract:
Enzymes are optimized to perform a particular chemical reaction in a given environment; even difficult transformations are efficient and amazingly specific. We work on enzymes that do interesting chemistry – where the reactions are unusual, depend upon transition metals, or occur under adverse conditions. An overall goal is to link an enzyme's chemical mechanism with its regulation in cells. A variety of biochemical, synthetic, spectroscopic, and kinetic techniques will be employed.
Desaturation. Iron- and O2-dependent enzymes catalyze many challenging oxidations, including the conversion of an unactivated alkane to an alkene that occurs during unsaturated lipid biosynthesis. These desaturases are closely related to metalloenzymes that form epoxides or alcohols from similarly inert substrates, but do not result in oxygen atom insertions. We aim to understand the non-heme iron-containing desaturase active site, the mechanism of double- and triple-bond formation, and how desaturase activity is affected by other cell components.
Acid tolerance. Bacteria that thrive in harsh environments contain many enzymes that could be useful drug targets or in "green" industrial chemical transformations. Enzymes from the acid-producing bacterium Acetobacter aceti can function at strikingly low internal pH, conditions not tolerated by many familiar enzymes. This harmless bacterium is naturally adept at sensing and counteracting the toxic effects of acid, an ability that many important pathogens have recently acquired. By studying enzymes from this organism and its response to high acid levels, we hope to learn the biochemical rules for life at low pH.
Selected Publications:
Kappock TJ, Ealick SE, Stubbe J. Modular evolution of the purine biosynthietic pathway. Curr Opin Chem Biol 2000 4:567-572.
Mathews II, Kappock TJ, Stubbe J, Ealick SE. Crystal structure of Escherichia coli PurE, an unusual mutase in the purine biosynthetic pathway. Structure 1999 7:1395-1406.
Meyer E, Kappock TJ, Osuji C, Stubbe J. Evidence for the direct transfer of the carboxylate of N5-carboxyaminoimidazole ribonucleotide (N5-CAIR) to generate 4-carboxy-5-aminoimidazole ribonucleotide catalyzed by Escherichia coli PurE, an N5-CAIR mutase. Biochemistry 1999 38:3012-3018.
Kappock TJ, Caradonna JP. Pterin-dependent amino acid hydroxylases. Caradonna Chem Rev 1996 96:2659-2756.
Kappock TJ, Harkins PC, Freidenberg S, Caradonna JP. Spectroscopic and kinetic properties of unphosphorylated rat hepatic phenylalanine hydroxylase expressed in Escherichia coli: Comparison of resting and activated states. J Biol Chem 1995 270:3053230544.
Last Updated: 01/07/2008 |