Riboflavin Directly Mediates the Dealkylation by Microbial Cytochrome P450 Monooxygeneses

As a vast repertoire of enzymes in nature, microbial cytochrome P450 monooxygenases require an activated form of flavin as a cofactor for the catalytic activity. Riboflavin is the precursor of FAD and FMN that serve as indispensable cofactors for flavoenzymes. In contrast to previous notion, here we describe the identification of an electron transfer process directly mediated by riboflavin for the N-dealkylation by microbial P450 monooxygenases. The electron relay from NADPH to riboflavin and then via activated oxygen to heme was proposed based on the combination of X-ray crystallography, molecular modeling and molecular dynamics simulation, site-directed mutagenesis and biochemical analysis of representative microbial P450 monooxygenases. This study provides new insights into the electron transfer mechanism in microbial P450 enzyme catalysis and likely in plants and mammals.