Professor John Lipscomb

Oxygenase enzymes utilize O₂ to oxidize a wide range of biological and manmade compounds with the incorporation of one or both atoms of oxygen into the products. These researchers are working on two projects that use MSI:

• The first project studies a series of dioxygenase enzymes. These enzymes attack aromatic compounds. The products are ring open compounds containing both atoms of oxygen from O₂. These products are easily degraded by bacteria, thus allowing the enormous amounts of carbon stored in aromatic compounds in the environment to reenter the carbon cycle. Also, the dioxygenases allows manmade aromatics, some of which are carcinogens, to be degraded. In collaboration with Professors Doug Ohlendorf and Carrie Wilmot, these researchers have solved the crystal structures of three of these enzymes. MSI is being used to examine the crystal structures and to plan site directed mutagenesis studies. The researchers have also recently been able to structurally characterize the first reaction cycle intermediates in two classes of these enzymes by carrying out the reaction in a crystal and analyzing the data at MSI.
• The second class of oxygenase being studied is typified by methane monooxygenase (MMO). This enzyme catalyzes the oxidation of methane to methanol with the incorporation of one atom of oxygen. Methane is generated in large quantities in the environment and is a potent greenhouse gas. It is prevented from reaching the atmosphere by the action of MMO. With Professor Ohlendorf, this group solved the crystal structure of the critical hydroxylase component and MSI is being used to visualize the structure and plan mutagenesis studies. Recently, the researchers have discovered two new members of this family that are responsible for the biosynthesis of many antibiotics. The structures of these enzymes have recently been solved by analyzing data using MSI. Structural studies of the substrate complexes and reaction cycle intermediates are planned. Most recently, work using MSI involves the analysis of data obtained of microcrystals of the complex between two components of MMO which act together to catalyze the methane oxidation reaction. The structure of the complex was solved using an X-ray free electron laser (XFEL) which yields diffraction data on a femtosecond time scale. This ultrashort time scale will potentially allow the structures of reaction cycle intermediates to be solved as they are formed in a single turnover cycle.