Abstract
BACKGROUND: Accurate determination of cholesterol requires complete hydrolysis of cholesteryl esters and must be very fast for the kinetic cholesterol assay. We investigated the properties of cholesterol esterase derived from Pseudomonas fluorescens, Candida cylindracea, bovine pancreas, and porcine pancreas for cholesterol determination in human serum. METHODS: Optimization of four enzymes and effect of sodium cholate concentration were performed. We evaluated and compared their performances in enzymatic kinetic cholesterol determination. RESULTS: The optimal sodium cholate concentration was 3, 5, 15, and 12 mmol/l with the enzyme activities at 200, 100, 100, and 100 U/l for P. fluorescens, C. cylindracea, bovine pancreas, and porcine pancreas, respectively. Linearity obtained from all enzymes was up to 16.3 mmol/l. All assays were compared favorably with standardized endpoint method. Only the cholesterol esterase derived from porcine pancreas demonstrated acceptable precision within the acceptable criteria (%CV < 3.0). Also, this esterase was least affected by interfering substances and showed longer stability than that of C. cylindracea and bovine pancreas. CONCLUSION: Porcine pancreas cholesterol esterase is superior to that obtained from P. fluorescens, C. cylindracea, and bovine pancreas for total serum cholesterol determination by the kinetic method because of its lower cost, better accuracy and precision, less interference, and longer stability.