Compressibility and uncoupling of cytochrome P450cam: high pressure FTIR and activity studies

Protein electrodes with direct electrochemical communication

Electrochemistry using direct electron transfer between an electrode and a protein or an enzyme has developed into a means for studying biological redox reactions and for bioanalytics, biosynthesis and bioenergetics. This review summarizes recent work on direct protein electrochemistry with special emphasis on our results in bioelectrocatalysis using isolated enzymes and enzyme-protein couples.

The status of high-valent metal oxo complexes in the P450 cytochromes

The oxidative prowess of the P450 cytochromes in physiological reactions is attributed to the production of a high-valent iron-oxo complex, or Compound I intermediate, in the reaction cycle. Despite many years of study, however, the full electronic description of this fleeting intermediate still remains an active area of study. In this manuscript, the current status of the isolation and characterization of the P450 oxo-Fe(IV) is examined and compared to analogous states in related heme enzymes. In addition, the utilization of cofactor exchange to stabilize high-valent oxo-states in the P450 is addressed. Structural and spectroscopic studies on manganese reconstituted P450, and its corresponding oxo-complex, are presented.

Freeze-quenched iron-oxo intermediates in cytochromes P450

Since the discovery of cytochromes P450 and their assignment to heme proteins a reactive iron-oxo intermediate as the hydroxylating species has been discussed. It is believed that the electronic structure of this intermediate corresponds to an iron(IV)-porphyrin-pi-cation radical system (Compound I). To trap this intermediate the reaction of P450 with oxidants (shunt pathway) has been used. The common approaches are stopped-flow experiments with UV-visible spectroscopic detection or rapid-mixing/freeze-quench studies with EPR and Mössbauer spectroscopic characterization of the trapped intermediate. Surprisingly, the two approaches seem to give conflicting results. While the stopped-flow data indicate the formation of a porphyrin-pi-cation radical, no such species is seen by EPR spectroscopy, although the Mössbauer data indicate iron(IV) for P450cam (CYP101) and P450BMP (CYP102). Instead, radicals on tyrosine and tryptophan residues are observed. These findings are reviewed and discussed with respect to intramolecular electron transfer from aromatic amino acids to a presumably transiently formed porphyrin-pi-cation radical.

Cytochrome P450 biosensors—a review

Cytochrome P450 (CYP) is a large family of enzymes containing heme as the active site. Since their discovery and the elucidation of their structure, they have attracted the interest of scientist for many years, particularly due to their catalytic abilities. Since the late 1970s attempts have concentrated on the construction and development of electrochemical sensors. Although sensors based on mediated electron transfer have also been constructed, the direct electron transfer approach has attracted most of the interest. This has enabled the investigation of the electrochemical properties of the various isoforms of CYP. Furthermore, CYP utilized to construct biosensors for the determination of substrates important in environmental monitoring, pharmaceutical industry and clinical practice.