title: The use of xanthine oxidase for a specific and sensitive fluorimetric determination of 6-mercaptopurine in serum.
abstract: A specific and highly sensitive fluorimetric method was developed for the determination of 6-mercaptopurine (6MP) in serum. The method is based on the enzymatic oxidation of 6MP with xanthine oxidase to the oxypurine, followed by oxidation with acidic chromate to the corresponding 6-sulfonate. The fluorescent product has excitation and emission maxima at 330 and 400 nm, respectively. The limit of sensitivity was approximately 22 pg/ml for 6MP in water. The sensitivity limit for 6MP in serum containing azathioprine was approximately 2.2 ng/ml. The rate constants for conversion of 6MP into the final product (6-thiouric acid) and the apparent Michaelis constant were also determined by a nonlinear regression analysis based on the integrated Michaelis-Menten equation using the ultraviolet absorbance data and the simplified complementary tristimulus colorimetry.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007700:Kinetics; D015122:Mercaptopurine / Q000097:blood*; D010084:Oxidation-Reduction; D013050:Spectrometry, Fluorescence; D014527:Uric Acid / Q000031:analogs & derivatives / Q000096:biosynthesis; D014969:Xanthine Oxidase
chemical_list: D014527:Uric Acid; C010352:6-thiouric acid; D015122:Mercaptopurine; D014969:Xanthine Oxidase