Case Western Reserve University - 1974
University of Michigan - 1970
National Institutes of Health - 1978-1983
Baylor University - 1983-Present
National Institutes of Health - 1988, 1989, 1991
In biochemistry, the field of enzymology has broad applications: from fundamental questions of enzyme mechanism to the utilization of enzymes in numerous areas of biotechnology and the development of therapeutic agents by the pharmaceutical industry. Research in my laboratory is directed toward the investigation of enzymes involved in the formation and degradation of e-(g-glutamyl)lysine and g-glutamylpolyamine crosslinks in proteins with emphasis on mechanism of enzyme action, the purification and properties of individual enzymes, and the design and synthesis of enzyme inhibitors and substrates.
Transglutaminases are a widely distributed group of enzymes that catalyze covalent crosslinking of proteins and peptides through e-(g-glutamyl)lysine linkages and through di-g-glutamylpolyamine bonds. The catalytic power of these enzymes is required for the stabilization of fibrin clots during hemostasis, in wound healing, for crosslinking of membrane proteins during skin development, and in fertilization.
The role of transglutaminases in cell regulation including cell proliferation, and macrophage activation is currently being investigated. Specific inhibitors of Factor XIIIa, the transglutaminase of the blood clotting cascade, will be applied to the investigation of the physiological role of this enzyme and may prove useful as therapeutic agents in preventing thrombosis. We are using a model system to evaluate target compounds that are analogs of peptide substrates as enzyme inhibitors. We have developed a fluorometric HPLC assay for transglutaminase using a small synthetic compound and a fluorescent amine as substrates. We have extended this assay to evaluate additional peptide substrates including Substance P and endorphin.
The laboratory is equipped with a peptide synthesizer an HPLC, and an amino acid analyzer. NMR, FT-IR, high-resolution mass spectrometry and x-ray crystallography are also tools used to determine the structure of synthetic compounds. In studies designed to elucidate the catabolism of e-(g-glutamyl)lysine crosslinks and other biological products of the action of the enzyme transglutaminase, we discovered an enzyme, g-glutamylamine cyclotransferase (g-GACT) that can act on e-(g-glutamyl)lysine, g-glutamyl derivatives of putrescine, histamine, spermidine, spermine and amines to give 5-oxo-proline and free amine. To determine if this enzyme functions in the catabolism of crosslinked proteins, we are currently characterizing g-GACT with respect to its basis for specificity.