alpha-Methyldopa, alpha-methyldopamine an alpha-methylnoradrenaline: substrates for the thermolabile form of human platelet phenol sulphotransferase.
alpha-Methyldopa, alpha-methyldopamine an alpha-methylnoradrenaline: substrates for the thermolabile form of human platelet phenol sulphotransferase.
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α-甲基多巴、α-甲基多巴胺和 α-甲基去甲肾上腺素：人血小板苯酚磺基转移酶不耐热形式的底物。
DOI：
10.1111/j.1365-2125.1982.tb01967.x
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发表时间：
1982
影响因子：
3.4
通讯作者：
Weinshilboum,R
中科院分区：
文献类型：
--
作者：
Mwaluko,G;Weinshilboum,R
1苯酚磺基转移酶（PST）催化的硫酸盐结合是α-甲基多巴（MD）催化的重要途径。PST活性在一个容易获得的组织，如人血小板的变化可能反映了在其他器官和组织中的MD的硫酸盐结合的个体差异。至少有两种形式的人血小板PST，一种是以多巴胺为底物的热不稳定形式，另一种是以低浓度苯酚为底物的热稳定形式。2 MD、α-甲基多巴胺（MDA）和α-甲基去甲肾上腺素（MNA）作为人血小板PST的底物进行测试。所有这三种酶都是不耐热形式的酶的底物，没有一种是热稳定形式的PST的底物。MD、MDA和MNA的表观米氏（Km）值分别为5.5、0.014和0.28 mM。对于三种儿茶酚底物，反应的硫酸盐供体3 '-磷酸腺苷-5'-磷酸硫酸盐的表观Km值分别为0.08、0.13和0.10 μ M。反应的最适pH为7.5的MD和6.5的MDA和MNA。3.20例受试者的血小板匀浆中，用多巴胺测定的PST活性与用MD、MDA和MNA测定的PST活性之间存在显著的相关性（r分别为0.54、0.98和0.93，P <0.02、<0.001和<0.001），而低浓度酚与MD、MDA和MNA测定的活性之间无显著相关性（r分别为0.021、0.045和0.046）。这些结果也与MD、MDA和MNA是热不稳定型血小板PST的底物的结论一致。4这些观察结果将使人们有可能测试的假设，即在活动中的变化，热不稳定形式的血小板PST可能反映了个体差异的硫酸盐共轭的MD，MDA和MNA。
1 Sulphate conjugation catalyzed by phenol sulphotransferase (PST) is an important pathway in the catabolism of alpha‐methyldopa (MD). Variations in PST activity in an easily obtained tissue such as the human platelet might reflect individual differences in the sulphate conjugation of MD in other organs and tissues. There are at least two forms of human platelet PST, a thermolabile form for which dopamine is a substrate and a thermostable form for which low concentrations of phenol can serve as a substrate. 2 MD, alpha‐methyldopamine (MDA) and alpha‐methylnoradrenaline (MNA) were tested as substrates for human platelet PST. All three were substrates for the thermolabile form of the enzyme and none were substrates for the thermostable form of PST. Apparent Michaelis‐Menten (Km) values for MD, MDA and MNA were 5.5, 0.014 and 0.28 mM, respectively. Apparent Km values for 3'‐ phosphoadenosine‐5'‐phosphosulphate, the sulphate donor for the reaction, were 0.08, 0.13 and 0.10 microM, respectively, for the three catechol substrates. The pH optima for the reaction were 7.5 for MD and 6.5 for both MDA and MNA. 3 When platelet homogenates from 20 individual subjects were tested, there were significant correlations between PST activities measured with dopamine and those measured with MD, MDA and MNA (r = 0.54, 0.98 and 0.93, P less than 0.02, less than 0.001, and less than 0.001, respectively), but not between activities measured with low concentrations of phenol and those measured with MD, MDA and MNA (r = 0.021, 0.045 and 0.046, respectively). There results were also compatible with the conclusion that MD, MDA and MNA were substrates for the thermolabile form of platelet PST. 4 These observations will make it possible to test the hypothesis that variations in the activity of the thermolabile form of platelet PST may reflect individual differences in the sulphate conjugation of MD, MDA and MNA.