THE CHEMICALLY INDUCIBLE PLANT CYTOCHROME-P450 CYP76B1 ACTIVELY METABOLIZES PHENYLUREAS AND OTHER XENOBIOTICS

Cytochrome P450s (P450s) constitute one of the major classes of enzyme s that are responsible for detoxification of exogenous molecules both in animals and plants. On the basis of its inducibility by exogenous c hemicals, we recently isolated a new plant P450, CYP76B1, from Jerusal em artichoke (Helianthes tuberoses) and showed that it was capable of dealkylating a model xenobiotic compound, 7-ethoxycoumarin. In the pre sent paper we show that CYP76B1 is more strongly induced by foreign co mpounds than other P450s isolated from the same plant, and metabolizes with high efficiency a wide range of xenobiotics, including alkoxycou marins, alkoxyresorufins, and several herbicides of the class of pheny lureas. CYP76B1 catalyzes the double N-dealkylation of phenylureas wit h turnover rates comparable to those reported for physiological substr ates and produces nonphytotoxic compounds. Potential uses for CYP76B1 thus include control of herbicide tolerance and selectivity, as well a s soil and groundwater bioremediation.