CHARACTERIZATION OF THE N-DEMETHYLATION REACTIONS CATALYZED BY CHLOROPEROXIDASE

Abstract

Publisher Summary This chapter describes the characterization of the N -demethylation reactions catalyzed by chloroperoxidase (CPO). CPO is a monomeric hemeprotein isolated from the mold Caldariomyces fumago. Like cytochrome P-450, CPO forms a reduced + CO complex having the maximum of the Soret band at an unusually long wavelength, approximately 443 nm. Studies using Mossbauer, MCD, and EPR spectroscopy have demonstrated that CPO exhibits a number of unusual physicochemical properties similar to those of the bacterial and microsomal P-450-type cytochromes. The striking physicochemical similarities between CPO and cytochrome P-450 have led to suggest that the two proteins may provide similar environments for the heme active site. This chapter presents the results of a study of CPO-catalyzed N-demethylation, a characteristic reaction of liver microsomal cytochrome P-450, which demonstrates the catalytic similarities between the two proteins. When EtOOH is used as the oxidant, the rate of formation of formaldehyde is linear for more than 20 min under the conditions used for these studies. HPLC analysis of the reaction mixture indicates that N -methylaniline is the major amine product formed and no other side-products are produced in significant amounts during the course of the reaction.