人血小板作为硫酸结合反应的独立单位。

The human platelet as an independent unit for sulfate conjugation.

作者信息

Khoo B Y, Sit K H, Wong K P

机构信息

Department of Biochemistry, National University of Singapore.

出版信息

Life Sci. 1988;42(11):1165-71. doi: 10.1016/0024-3205(88)90612-1.

DOI:10.1016/0024-3205(88)90612-1

PMID:3347145

Abstract

The human platelets possess a full complement of enzymes capable of synthesizing N-acetyldopamine (NADA) 35sulfate from ATP, Mg++ and sodium 35sulfate. The pH optimum for this three-step overall sulfate conjugation (comprising of the ATP sulfurylase, APS kinase and phenolsulfotransferase reactions) is 8.6 and the reactions proceeded progressively for several hours. Both ATP and Mg++ ions, above their respective optimal concentrations of 5 and 7 mM, inhibited the sulfate conjugation of NADA. The apparent Km values for NADA as determined by the phenolsulfotransferase (PST) and overall reactions were similar in magnitude being 2.6 and 4.8 microM, respectively, while that for sodium 35sulfate was 202 microM. A comparison of these two activities in 62 platelet preparations of normal subjects showed that the rate of the PST reaction was generally higher than the overall reaction even though the PST assay was carried out at suboptimal concentration of PAPS. There was a positive correlation (r = 0.82) between the two sets of data, suggesting that the PST reaction probably has some control over the rate of overall sulfate conjugation.

摘要

人类血小板含有一整套能从ATP、Mg++和35硫酸钠合成N-乙酰多巴胺（NADA）35硫酸盐的酶。这种三步总体硫酸盐结合反应（由ATP硫酸化酶、APS激酶和酚磺基转移酶反应组成）的最适pH值为8.6，反应可持续数小时。ATP和Mg++离子在各自的最佳浓度（5 mM和7 mM）以上时，会抑制NADA的硫酸盐结合。酚磺基转移酶（PST）反应和总体反应测定的NADA表观Km值大小相似，分别为2.6和4.8 microM，而35硫酸钠的表观Km值为202 microM。对62份正常受试者血小板制剂中的这两种活性进行比较发现，即使PST测定是在PAPS亚最佳浓度下进行的，但PST反应速率通常仍高于总体反应速率。两组数据之间存在正相关（r = 0.82），表明PST反应可能对总体硫酸盐结合速率有一定的控制作用。