Cupin Dioxygenases: Role of Metal Center in Oxygen Activation

Arizona State University, Scottsdale AZ

Investigators

Abstract

Aerobic organisms have evolved to use the oxidizing potential of oxygen to their benefit. Although a powerful oxidizing agent, the direct reaction of dioxygen with other molecules is slow and nature has developed ways to lower this kinetic barrier. This process of oxygen activation has tremendous importance and the understanding of the principles by which this activation is accomplished is crucial. A new tool for the study of oxygen activation was recently introduced and involves the analysis of the effects of pH, viscosity, temperature, and isotopic composition on the second order rate constant for the reaction of dioxygen with an enzyme. Such studies have already provided valuable information on the nature of the rate-determining steps in oxygen activation in a number of enzyme systems. This project describes efforts towards the elucidation of the role of the metal center in the mechanism of oxygen and substrate activation in a group of dioxygenases belonging to the cupin superfamily. Two types of enzyme systems have been chosen for initial studies: copper-and iron-containing flavonol 2,3-dioxygenases from Aspergillus flavus and Bacillus subtilis, and nickel- and iron-containing acireductone dioxygenases from Klebsiella pneumoniae. These enzymes were chosen for their unique mechanisms and the potential to provide important insights into the mechanism of oxygen and substrate activation. Understanding of the structural basis for the catalytic diversity observed in the cupin superfamily of proteins may provide the foundation for deciphering the function of new protein members. Broader Impact: This project incorporates tools and techniques of biochemistry, bioinformatics,molecular biology,physical and synthetic organic chemistry, in the study of the mechanism of metalloenzymes. This multidisciplinary research provides an excellent opportunity for the education of graduate and advanced undergraduate students in a multicultural research environment that will foster mentoring of minority students.