The major thrust of my research lies at the crossroads of chemistry and biology. My group is currently working in four general research areas with focus on both elucidation of the mechanisms of novel enzymatic reactions and designing methods to control and/or manipulate enzymatic functions.
Using a multi-faceted approach, we study the mechanisms of enzymes carrying out novel cofactor-dependent reactions, reactions requiring metals for catalysis, and reactions involving catalytically relevant radical intermediates. Extensive structural (X-ray, NMR) and spectroscopic methods (EPR, Resonance Raman, NMR) are employed in our studies. A significant effort is also devoted to the organic synthesis of compounds as mechanistic probes or specific inhibitors for these biological catalysts. Enzymes currently under investigation participate in diverse biological processes such as the biosynthesis of various polyketide-derived natural products, isoprenoid biosynthesis, lipid metabolism and modification, unusual sugar biosynthesis, and post-translational modification of proteins. Many of these enzymes are potential drug targets.
We are interested in elucidating the pathways of unusual sugar biosynthesis and studying the mechanisms of novel enzymatic reactions in the pathways. We are also probing the functions of the glycosyltransferases and working to define the substrate flexibilities of these enzymes in an effort to generate new glycosylated compounds both in vivo and in vitro. We have demonstrated the feasibility of engineering sugar biosynthetic machinery in producing organisms and of in vitro glycosylation of substrate libraries to produce new macrolides carrying designed sugar appendages. Such combinatorial biosynthetic approaches hold great promise for finding compounds with new or improved biological activities. Studies of unusual sugar biosynthesis have also yielded several mechanistically interesting enzymes which are currently under detailed investigation.
Natural product biosynthetic pathways are a rich source of mechanistically interesting enzymatic transformations. Our group studies the biosynthesis of several novel natural products, including two involving polyketide cross-bridging reactions. These cyclization reactions may be catalyzed by enzymes potentially operating via a mechanism mimicking the Diels-Alder reaction. We are using a multidisciplinary approach to study the functions of these enzymes and establish their chemical mechanisms.
We study the biological function and mechanism of regulation of human poly(ADP-ribose) polymerase 1 (PARP-1), an enzyme that recognizes damaged DNA and activates repair mechanisms through poly(ADP-ribosyl)ation of itself and many relevant proteins. PARP-1 is also known to be involved in caspase-dependent apoptosis. We are interested in understanding the effect of self-modification on PARP-1 activity as well as identifying the in vivo protein substrates of PARP-1. We use combined chemical, biochemical, genetic, and high-throughput screening approaches to address these questions.
My group is motivated by the challenge and excitement of understanding these interesting biological transformations and by devising ways to control and/or manipulate them using both chemical and biological approaches.