Relative and absolute quantitative expression profiling of cytochromes P450 using isotope-coded affinity tags

Area of Science:

• Proteomics
• Analytical Chemistry
• Biochemistry

Background:

• Accurate protein quantification is crucial for understanding biological processes and drug development.
• Current methods for profiling proteins, especially cytochrome P450 enzymes, are often low-throughput and lack discriminatory power.
• Hydrophobic proteins and closely related isoforms present significant challenges for traditional 2-D gel electrophoresis and quantification.

Purpose of the Study:

• To develop and validate a novel method for absolute protein quantification using isotope-coded affinity tagging (ICAT).
• To apply this method for the high-throughput and discriminatory analysis of cytochrome P450 (P450) enzymes.
• To demonstrate the utility of ICAT technology in drug safety evaluation by assessing P450 induction profiles.

Main Methods:

• Development of a novel absolute protein quantification method utilizing isotope-coded affinity tagging (ICAT) reagents.
• Exploitation of synthetic peptide standards for precise protein content determination at the femtomole level.
• Application of ICAT for relative and absolute quantification of microsomal metabolic enzymes, specifically cytochromes P450.

Main Results:

• The ICAT method achieves absolute protein quantification at the femtomole level in biological samples.
• The technology demonstrates superior discriminatory power and throughput compared to conventional methods for P450 profiling.
• Distinct induction profiles for specific cyp2c subfamily members (e.g., cyp2c29) in response to phenobarbitone were simultaneously detected.

Conclusions:

• ICAT technology offers a rapid, widely applicable, and highly discriminatory approach for protein quantification.
• This method significantly enhances drug safety evaluation by enabling efficient measurement of P450 induction profiles.
• The technology has the potential to accelerate the drug development pathway through improved protein analysis capabilities.