T. J. Kappock

Assistant Professor of Biochemistry

Department: Biochemistry
Phone: 765.494.8383
Fax: 765.494.7897
Office: BCHM 29
E-mail: tkappock@purdue.edu

Area of Expertise: Resistance strategies in acetic acid bacteria; enzyme mechanism
Curriculum Vitae

Lab Members

St. Louis Business Journal - January 7, 2005

Enzyme mechanism. Enzymes are the gold standard for synthetic chemistry. We are particularly interested in those that form carbon-carbon bonds, among them the purine biosynthesis enzyme PurE and the citric acid cycle enzyme citrate synthase. An example of this remarkable chemistry is the CO₂ migration performed by PurE (illustrated below). Structural, mutagenesis, and pre-steady state kinetics methods are enlisted to understand how these enzymes do their jobs.

Biochemistry of acetic acid bacteria. Bacteria cope with life in harsh environments using specific stress responses and chemical alterations of cell components. The naturally acid-resistant bacterium Acetobacter aceti has the ability to handle low pH in general -- its cytoplasmic pH can drop to 4 -- and acetic acid in particular, which is quite toxic to bacteria at low pH. Acetic acid is formed in large amounts by acetic acid bacteria, a group of Gram-negative, plant-associated organisms used for millenia in the production of vinegar. We use this food-grade organism to define microbial acid survival strategies, some of which have been adopted by pathogens.

Our approach to this problem is centered on enzyme function at low pH, assisted by several in-progress genome sequencing projects. We found that individual A. aceti enzymes retain function in acid much longer than comparable forms from non-acidophilic organisms. X-ray crystallography has revealed distinctive architectural features of A. aceti proteins that may confer this stability. We have also delineated metabolic strategies for acetic acid elimination by highly-resistant strains, which may be employed by other microbes including several pathogens.

This material is based upon work supported by the National Science Foundation under Grant No. MCB 0936108. Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).

- Recent Publications

Mullins, E. A., & Kappock, T. J. (2013). Functional analysis of the acetic acid resistance (aar) gene cluster in Acetobacter aceti strain 1023. Acetic Acid Bacteria, s1, e3. Retrieved from http://www.pagepressjournals.org/index.php/aab/article/view/aab.2013.s1.e3

Mullins, E. A., & Kappock, T. J. (2012). Crystal structures of Acetobacter aceti succinyl-Coenzyme A (CoA):acetate CoA-transferase reveal specificity determinants and illustrate the mechanism used by class I CoA-transferases. Biochemistry, 42, 8422-8434. Retrieved from http://pubs.acs.org/doi/pdf/10.1021/bi300957f

Mullins, E. A., Starks, C. M., Francois, J. A., Sael, L., Kihara, D., & Kappock, T. J. (2012). Formyl-coenzyme A (CoA):oxalate CoA-transferase from the acidophile Acetobacter aceti has a distinctive electrostatic surface and inherent acid stability. Protein Sci., 21, 686-696. Retrieved from http://dx.doi.org/10.1002/pro.2054

Tranchimand, S., Starks, C. M., Mathews, I. I., Hockings, S. C., & Kappock, T. J. (2011). Treponema denticola PurE is a bacterial AIR carboxylase. Biochemistry, 50, 4623-4637. Retrieved from http://dx.doi.org/10.1021/bi102033a

Kurz, L. C., Constantine, C. Z., Jiang, H., & Kappock, T. J. (2009). The partial substrate dethiaacetyl-coenzyme A mimics all critical carbon acid reactions in the condensation half-reaction catalyzed by Thermoplasma acidophilum citrate synthase. Biochemistry, 48, 7878-7891. Retrieved from http://dx.doi.org/10.1021/bi9006447

Mullins, E. A., Francois, J. A., & Kappock, T. J. (2008). A specialized citric acid cycle requiring succinyl-coenzyme A (CoA):acetate CoA-transferase (AarC) confers acetic acid resistance on the acidophile Acetobacter aceti. J Bacteriol, 190, 4933-4940. Retrieved from http://dx.doi.org/10.1128/JB.00405-08

Francois, J. A., & Kappock, T. J. (2007). Alanine racemase from the acidophile Acetobacter aceti. Protein Expr. Purif., 51, 39-48. Retrieved from http://dx.doi.org/10.1016/j.pep.2006.05.016

Schaefer, J., Jiang, H., Ransome, A. E., & Kappock, T. J. (2007). Multiple active site histidine protonation states in Acetobacter aceti N5-carboxyaminoimidazole ribonucleotide mutase detected by REDOR NMR. Biochemistry, 46, 9507-9512. Retrieved from http://dx.doi.org/10.1021/bi700899q

Constantine, C. Z., Starks, C. M., Mill, C. P., Ransome, A. E., Karpowicz, S. J., Francois, J. A., . . . Kappock, T. J. (2006). Biochemical and structural studies of N5-carboxyaminoimidazole ribonucleotide mutase from the acidophilic bacterium Acetobacter aceti. Biochemistry, 45, 8193-8208. Retrieved from http://dx.doi.org/10.1021/bi060465n