人红细胞硫嘌呤甲基转移酶：放射化学微量测定法及生化特性

Human erythrocyte thiopurine methyltransferase: radiochemical microassay and biochemical properties.

作者信息

Weinshilboum R M, Raymond F A, Pazmiño P A

出版信息

Clin Chim Acta. 1978 May 2;85(3):323-33. doi: 10.1016/0009-8981(78)90311-x.

Abstract

A radiochemical micromethod for the determination of thiopurine methyltransferase (TPMT) activity in human red blood cells (RBC) is described. Both 6-mercaptopurine and 6-thioguanine were substrates for the TPMT activity in the human RBC. Apparent Michaelis-Menten (KM) values for 6-mercaptopurine and 6-thioguanine were 3.2 X 10(-4) M and 2.0 X 10(-4) M, respectively. The apparent KM value for S-adenosyl-L-methionine, a co-substrate for the reaction, was 1.7 X 10(-6) M. The pH optimum for the reaction was approximately 7.5. Blood samples from 73 randomly selected adult subjects had a mean activity of 10.2 +/- 2.4 (mean +/- S.D.) units/ml packed red blood cells. The range of activities was from 4.6 to 14.2 units/ml. The results of experiments in which partially purified human kidney TPMT was added to RBC lysates and of experiments in which "low" and "high" activity lysates were mixed gave no indication that individual variations in RBC TPMT activity were due to endogenous inhibitors or activators of the enzyme.

摘要

本文描述了一种用于测定人红细胞（RBC）中硫嘌呤甲基转移酶（TPMT）活性的放射化学微量方法。6-巯基嘌呤和6-硫鸟嘌呤均为人红细胞中TPMT活性的底物。6-巯基嘌呤和6-硫鸟嘌呤的表观米氏常数（KM）值分别为3.2×10⁻⁴ M和2.0×10⁻⁴ M。反应的共底物S-腺苷-L-甲硫氨酸的表观KM值为1.7×10⁻⁶ M。反应的最适pH约为7.5。从73名随机选择的成年受试者采集的血样中，每毫升压积红细胞的平均活性为10.2±2.4（平均值±标准差）单位。活性范围为4.6至14.2单位/毫升。将部分纯化的人肾TPMT添加到红细胞裂解物中的实验结果，以及将“低”活性和“高”活性裂解物混合的实验结果，均未表明红细胞TPMT活性的个体差异是由于该酶的内源性抑制剂或激活剂所致。