Structure and function of dioxygenases. One approach to lignin degradation

The evolution of biosynthetic pathways leading to the formation of those structural natural products found in higher plants occurred in an oxygen-rich environment. Mixed function oxygenases evolved and functioned in catalyzing the insertion of molecular oxygen into basic structural polymers such as lignin, as well as natural products such as flavanoids and alkaloids. In addition to the critical role played by molecular oxygen in biosynthesis, oxidative degradative pathways evolved for the return of these natural products to the carbon cycle in the form of carbon dioxide. Oxidative degradation of natural products occurs by oxygen insertion reactions which are catalyzed by the mixed function oxygenases and by the dioxygenases. Reaction mechanisms for the mixed function oxygenases are now quite well understood, and a number of chemical model systems have been designed which catalyze such oxidation reactions. However, at the present time we do not have enough pertinent information on the mechanism of action of dioxygenases. This report provides some information to allow for the design of chemical model systems which mimic dioxygenase activity.