Human erythrocyte phenol O-methyltransferase: radiochemical microassay and biochemical properties.
Human erythrocyte phenol O-methyltransferase: radiochemical microassay and biochemical properties.
复制标题
人红细胞酚 O-甲基转移酶：放射化学微量测定和生化特性。
DOI：
10.1016/0009-8981(78)90331-5
复制
发表时间：
1978
期刊：
影响因子：
--
通讯作者：
R. Weinshilboum
中科院分区：
文献类型：
--
作者：
P. Pazmiño;R. Weinshilboum
已经开发出一种用于测定人红细胞膜中苯酚甲基转移酶（PMT）活性的放射化学微量测定法。对乙酰氨基酚用作底物。对乙酰氨基酚的表观米氏 (KM) 值为 21.2 × 10−3M。反应共底物 S-腺苷-L-甲硫氨酸的表观 KM 值为 4.8 × 10−6M，四种不同缓冲系统的最佳反应 pH 值约为 9.0。苯酚也作为底物进行了测试，其表观 Km 值为 2.0 × 10−3M。人红细胞（RBC）膜PMT活性不具有儿茶酚O-甲基转移酶（另一种红细胞膜甲基转移酶活性）的生化特征。从 212 名随机选择的成年白人受试者中获得的血液样本的平均活性为每小时每毫克蛋白质形成 134.5 ± 41.5 pmol 对乙酰苯胺（平均值 ± S.D.）。活动数量从 44 到 282 个不等。男性和女性样本的平均活动没有差异。对“低”和“高”活性红细胞膜制剂的混合物进行 PMT 测定的实验没有证据表明酶活性的变化是由于内源性 PMT 激活剂或抑制剂的存在造成的。 9 名肾衰竭患者（一种酚类循环水平升高的病理状态）血液中红细胞膜 PMT 活性显着降低，平均活性为 76.2 ± 9.7（平均值 ± S.E.M.，P< 0.001）。
A radiochemical microassay for the determination of phenolO-methyltransferase (PMT) activity in human red blood cell membranes has been developed. Acetaminophen was used as the substrate. The apparent Michaelis-Menten (KM) value for acetaminophen was 21.2 × 10−3M. The apparentKMvalue forS-adenosyl-L-methionine, a co-substrate for the reaction, was 4.8 × 10−6M, and the pH optimum of the reaction was approximately 9.0 with four different buffer systems. Phenol was also tested as a substrate and had an apparentKmvalue of 2.0 × 10−3M. Human erythrocyte (RBC) membrane PMT activity did not have the biochemical characteristics of catecholO-methyltransferase, another RBC membrane methyltransferase enzyme activity. Blood samples obtained from 212 randomly selected adult white subjects had a mean activity of 134.5 ± 41.5 pmol ofp-acetanisidide formed per mg protein per hour (mean ± S.D.). Activities varied from 44 to 282 units. There were no differences in the mean activities of samples from men and women. Experiments in which mixtures of “low” and “high” activity RBC membrane preparations were assayed for PMT provided no evidence that the variations in enzyme activity were due to the presence of endogenous PMT activators or inhibitors. RBC membrane PMT activity in blood from 9 patients with renal failure, a pathological state in which there are elevated circulating levels of phenols, was found to be significantly decreased with average activity of 76.2 ± 9.7 (mean ± S.E.M.,P< 0.001).