Engineering of a functional human NADH-dependent cytochrome P450 system

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Cytochrome P450 enzymes are crucial for drug metabolism and detoxification.
• Human NADPH cytochrome P450 reductase (CPR) is the essential redox partner for P450 enzymes, utilizing NADPH as its cofactor.
• Altering CPR's cofactor preference could create novel enzymatic systems for research and therapeutic applications.

Purpose of the Study:

• To engineer a functional human NADH-dependent cytochrome P450 system.
• To investigate the role of Trp-676 in CPR's cofactor specificity.
• To characterize the kinetic properties of the engineered NADH-dependent CPR mutant.

Main Methods:

• Site-directed mutagenesis was used to substitute Trp-676 in human CPR.
• Enzyme activity was assessed by measuring the reduction of cytochrome c and ferricyanide.
• Metabolism of 7-ethoxyresorufin by CYP1A2 was used to evaluate the functional P450 system.
• Kinetic parameters (kcat, KM) were determined for the wild-type and mutant CPR enzymes.

Main Results:

• A single amino acid substitution (W676A) in human CPR created a functional NADH-dependent enzyme.
• The W676A mutant exhibited high specificity for NADH, with catalytic efficiency comparable to wild-type CPR using NADPH.
• The engineered enzyme successfully metabolized 7-ethoxyresorufin via CYP1A2 and showed altered substrate affinities for both NADH and NADPH.
• Structural integrity and 2'-AMP binding were unaffected by the W676A mutation.

Conclusions:

• Trp-676 is critical for cofactor discrimination in human CPR.
• Substitution of Trp-676 with alanine yields an efficient NADH-dependent cytochrome P450 system.
• This engineered system offers a valuable tool for biochemical studies and potential therapeutic interventions.