Thiopurine Methyltransferase (TPMT), Erythrocytes
Method Description Describes how the test is performed and provides a method-specific reference
Thiopurine methyltransferase (TPMT) catalyzes the metabolism of 6-mercaptopurine to 6-methylmercaptopurine (6-MMP) in erythrocytes, utilizing S-adenosyl-L-methionine as the methyl group. The rate of formation of 6-MMP is an indication of the amount of TPMT present in a patient's red blood cell lysate. Reactions that would interfere with the specific TPMT methylation, such as nonenzymatic methylation of 6-MMP and the formation of methylthiopurines other than 6-MMP, are eliminated: Km (Michaelis constant)-appropriate substrate concentrations are employed in a batched reagent to reduce nonenzymatic methylation. Phosphate buffers are used because other buffers allow for the formation of methylthiopurines other than 6-MMP.(Lacey JM, Magera MJ, Matern D, O'Brien JF: Quantitation of 6-methylmercaptopurine for the determination of thiopurine methyltransferase; unpublished Mayo manuscript)
PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday, Wednesday through Friday; Varies