Michael T. Green

Biological, Inorganic, and Physical Chemistry

The Green group uses a mixture of theory and experiment to investigate the factors that determine enzymatic reactivity. One area of focus is the role of thiolate ligands in oxidative heme chemistry. Thiolate-ligated heme proteins play critical roles in a number of important physiological processes (e.g. the metabolism of xenobiotics, neurotransmission, blood pressure control, and immune defense against tumor cells). Thiolate-ligated heme enzymes are unique in that they catalyze the insertion of an oxygen atom, derived either from molecular oxygen or peroxide, into a variety of organic substrates, often with high degrees of regio- and stereo-selectivity. The natural function of non-thiolate ligated systems generally involves one-electron rather than two-electron oxidations or oxygen transfer reactions. We are trying to understand what factors determine the ability of these enzymes to transfer oxygen. The hope is that knowledge gained from these investigations can be used to guide protein or catalyst design, so that the synthetic potential of these reactions can be realized in industrial applications. Another area of interest is selenium containing proteins. Selenium's role as an essential micronutrient first became apparent in 1957, but it was not until 1973, with the discoveries of the first selenoproteins, that a biochemical explanation for its beneficial effects became available. Since then, over 30 such proteins have been identified, many of these only in the last decade. Some of these enzymes have fascinating post-translational modifications and active-sites that contain other trace biological elements. The role of selenium in most of these systems is not well understood. Our current investigations focus on how local environment and substrate preference determine the choice of this element.