Enantiomeric discrimination of Ru-substrates by cytochrome P450 cam

Abstract

Molecules with photosensitizers attached to substrates (Wilker et al., Angew. Chem. Int. Ed. 38 (1999) 90–92) or cofactors (Hamachi et al., J. Am. Chem. Soc. 121 (1999) 5500–5506) can rapidly deliver redox equivalents to buried active sites. The structure of cytochrome P450 cam (P450) co-crystallized with a prototypal sensitizer-substrate, [Ru-C 9-Ad]Cl 2, has been determined (Dmochowski et al., Proc. Natl. Acad. Sci. USA 96 (1999) 12987–12990); and, in separate UV–vis absorption and time-resolved luminescence experiments, the binding of the Λ and Δ enantiomers of Ru-C 9-Ad to P450 has been measured. The results, K D(Δ/Λ)∼2, indicate that the bipyridyl ligands of the Λ isomer interact more favorably with hydrophobic residues at the entrance to the substrate channel. We conclude that enantiospecific interactions may be exploited in the design of enzyme-metallosubstrate conjugates.