Enzyme Kinetics of 6 Specific Substrates of Cytochrome P_(450) Enzymes / 中国药房

ABSTRACT

OBJECTIVE:To study the enzyme kinetics of six specific substrates of cytochrome P450 enzymes. METHODS: The transforming amount of the corresponding metabolites of six substrates was determined by LC-MS/MS. The incubation conditions of substrates in human liver microsomes were optimized and the parameters of enzyme kinetics were calculated based on substrate concentration-reaction velocity curve. RESULTS: The optimal incubation time was 20 min and the optimal enzyme concentration was 0.25 mg protein?mL-1. The Km(?mol?L-1) values of phenacetin, tolbutamide, omeprazole, dextromethorphan,chlorzoxazone and nifedipine were 21.6,163.4,10.4,4.6,41.9 and 9.4 respectively. The Vmax (nmol?min-1?mg protein-1) values were 2.08, 0.52, 1.02, 0.40, 2.36 and 1.00 respectively. CONCLUSION: The enzyme kinetics of six specific substrates of cytochrome P450 enzymes has been investigated in this study, and the study serves as a reference and support for the study and application of substrates in CYP.