Bioelectronically Initiated Cyt P450s Catalysis without NADPH

Abstract

The catalytic cycle of cytochrome P450s (cyt P450s) features delivery of electrons from NADPH to cyt P450 reductase (CPR) for subsequent delivery to cyt P450 heme. Attempts at bioelectronic initiation of cyt P450s catalysis have been made by replacing the electron donation from expensive NADPH by other electron donnors. 1 To this aim, an electrode-driven drug metabolism biosensors were constructed with a mixed film containing ITO nanoparticles and CYP2C9/CPR-microsomes encapsulated by chitosan (CS) on a GC electrode. The electrochemical response of the enzyme modified electrode to 4-hydroxylation of tolbutamide has been validated, which allowed rapid determination of the affinity parameter Km appat 202.84 μM. The inhibition effect of sulfaphenazole on the CYP2C9-dependent 4-hydroxylation of tolbutamide was also investigated. Quantum dots (QDs), a kind of semiconductor materials, can also act as electron donnors. Based on the photo-induced electron transfer (PET) from QDs to the hemoproteins, a photoelectrochemical biosensor for the light-controlled drug metabolism by cyt P450s was then constructed. As shown in scheme 1, the photosensitized QDs offer electrons demanded in the cyt P450 catalytic process while the electrode at appropriate bias potentials acts as an electron supplier to QDs for neutralizing the VB holes and monitors the occurrence of the light-induced catalytic process. This novel biosensor can be applied in drug discovery and development by monitoring substrate metabolism and enzyme inhibition.