Current state and future perspectives of cytochrome P450 enzymes for C–H and C=C oxygenation

Cytochrome P450 enzymes (CYPs) catalyze a series of C–H and C=C oxygenation reactions, including hydroxylation, epoxidation, and ketonization. They are attractive biocatalysts because of their ability to selectively introduce oxygen into inert molecules under mild conditions. This review provides a comprehensive overview of the C–H and C=C oxygenation reactions catalyzed by CYPs and the various strategies for achieving higher selectivity and enzymatic activity. Furthermore, we discuss the application of C–H and C=C oxygenation catalyzed by CYPs to obtain the desired chemicals or pharmaceutical intermediates in practical production. The rapid development of protein engineering for CYPs provides excellent biocatalysts for selective C–H and C=C oxygenation reactions, thereby promoting the development of environmentally friendly and sustainable production processes.

Electron transfer and oxidase activities in reconstituted hemoproteins with chemically modified cofactors

Protoheme IX is a typical iron porphyrin cofactor, showing a variety of reactivities in many hemoproteins under the reaction environments provided by protein matrices. Chemical modification of the protoheme cofactor is expected to be a versatile strategy to design hemoproteins possessing unique functions. This review focuses on the conversion of a hemoprotein, mainly myoglobin (an oxygen-storage hemoprotein), into a protein having different functions from the original ones by replacement of the protoheme cofactor with synthetic cofactors. The myoglobin having anionic patches pended to the heme propionates effectively binds electron-accepting proteins or small cationic organic molecules on the protein surface, resulting in enhanced efficiency of the photoinduced electron transfers from the myoglobin to these electron acceptors. Furthermore, the peroxidase and peroxygenase activities are also enhanced due to the facile substrate accesses. The attachment of the chemically active moiety such as flavin at the heme terminal is also important to give P450-like function to the native myoglobin. The employment of a structural isomer of porphyrin as an artificial cofactor gives rise to remarkably high dioxygen affinity and peroxidase activity in myoglobin, and allows us to easily detect high-valent species of the porphyrin isomer in HRP. These examples provide a clear insight into hemoprotein modifications based on synthetic chemistry as well as genetic amino acid mutations.

[Synthesis and structure-function study of artificial nucleases on the basis of hemin conjugates with peptide fragments of cell differentiation factor HLDF]

A series of octa-hexapeptide fragments of HLDF and their conjugates with hemin were obtained by solid phase peptide synthesis. A relationship between the structure and the nuclease activity of the compounds was established. The effect of various factors (medium pH, the presence of metal ions, complexons, reducers, and buffer composition) on DNA destruction with hemin peptides was studied. Preliminary information confirming an oxidative mechanism of this process was obtained. The cleavage of plasmid DNA under the action of hemin peptides was studied by the methods of electron microscopy, gel electrophoresis, and atomic force microscopy.

The role of the heme propionates in heme biochemistry

There are numerous studies, relying on both experimental and theoretical observations, illustrating the active role of the heme propionates in regulating electron delivery to the iron center as well as biochemical properties of the heme. Evidences for this come from a wide variety of heme containing systems: cytochromes, heme peroxidases, globins, etc. Here, we shortly summarize these studies and revisit previous theoretical calculations (V. Guallar, M.H. Baik, S.J. Lippard, R.A. Friesner, Proc. Natl. Acad. Sci. USA 100 (2003) 6998-7002) where the propionate groups induced the delocalization of the spin density in the cytochrome P450cam putative active species, Compound I. We introduce novel data, obtained by means of mixed quantum mechanics and molecular mechanics methods, indicating a larger electron delocalization into the protein. We also present novel results based on the recent migration of spin density observed by Barrows et al. (T.P. Barrows, T.L. Poulos, Biochemistry 44 (2005) 14062-68) on an ascorbate peroxidase mutant. All this data strongly supports the importance of the propionate groups in tuning the heme electronic properties.