A P450 Harboring Manganese Protoporphyrin IX Generates a Manganese Analogue of Compound I by Activating Dioxygen
Keita Omura, Yuichiro Aiba, Kazuto Suzuki, Shinya Ariyasu, Hiroshi Sugimoto, Osami Shoji
Abstract
The self-sufficient cytochrome P450 102A1 (P450BM3), known for its highly efficient activation of molecular oxygen, was reconstituted with manganese protoporphyrin IX. This artificial enzyme (Mn-BM3) was found to catalyze the monooxygenation of various substrates by activating molecular oxygen. Investigation using mechanistic probes (i.e., radical clock substrates) revealed that hydroxylation by Mn-BM3 proceeds via a radical intermediate of the substrate, supporting the involvement of an “H atom abstraction/•OH recombination” mechanism, which is the commonly accepted mechanism for hydroxylation by P450s. A DFT study also indicated that the activation barrier of Mn-porphine in the rebound step is higher than that of Fe-porphine, consistent with the experimental results obtained in the radical clock experiment, wherein Mn-BM3 presents a slower rebound rate than that of heme-bound BM3.