The formation and the destruction of phosphate esters are catalyzed with remarkable efficiency by enzymes, at rates millions of times (or more) faster than the analogous uncatalyzed reactions. Our research seeks to understand this chemistry, and how enzymes achieve these remarkable rate accelerations. Some phosphatases utilize metal ions in catalysis, and we are interested in learning how coordination of the substrate to the metal center may alter its electronic structure, or its stability, or how coordination might change the mechanism of catalysis. Such enzymes include purple acid phosphatase, PP1, and alkaline phosphatase. In another project studying the protein tyrosine phosphatases, we are examining how motions of the protein catalyst may drive the catalytic reaction. These phosphatases do not utilize metal ions, but are some of the most efficient enzymes known, with rate accelerations of nearly twenty orders of magnitude compared to the uncatalyzed rates of the reactions they catalyze. In this project we are collaborating with Sean Johnson, our department's protein crystallographer, to obtain the structures of site-directed mutants to correlate structural information with other data.

We use a variety of mechanistic tools in our work, including isotope effects, thermodynamics, kinetics and linear free energy relationships; isotope tracer labeling, and NMR. Since we use a variety of synthesized substrates, and the isotope effect methodology requires isotopically labeled substrates, students learn a variety of synthetic, chromatographic and spectroscopic techniques as well.

:: Funding

Our studies of acyl and phosphoryl transfer are funded through the Institute of General Medical Sciences of the National Institutes of Health. The NIH grant abstract can be accessed through the NIH CRISP retrieval database.