大鼠皮肤中3'-磷酸腺苷-5'-磷酸硫酸酯（PAPS）的生物合成

Biosynthesis of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) in rat skin.

作者信息

Wong K O, Wong K P

机构信息

Department of Biochemistry, Faculty of Medicine, National University of Singapore, Kent Ridge.

出版信息

Biochem Pharmacol. 1994 Feb 9;47(3):477-83. doi: 10.1016/0006-2952(94)90178-3.

DOI:10.1016/0006-2952(94)90178-3

PMID:8117315

Abstract

A rapid and sensitive radiometric assay was developed for the measurement of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) biosynthesis in rat skin extract. The formation of PAP35S from sodium 35sulfate and ATP was quantified by the transfer of the 35sulfate to minoxidil by rat liver minoxidil sulfotransferase (MST). The assay is sensitive enough for the detection of as little as 2 pmol of PAP35S. The PAPS-generating system showed a pH optimum of 8.6, with an apparent Km value of 1 mM for the ATP-Mg2+ complex and 68 microM for sodium 35sulfate. ATP and Mg2+, present individually or together in equimolar concentrations, were inhibitory above 8 mM. Excess (or free) ATP was a competitive inhibitor with respect to the ATP-Mg2+ complex; the apparent Ki measured was 0.32 mM. The specific activity of the PAPS-generating system, measured in rat skin cytosol was 0.15 nmol PAPS/min/mg protein. The importance of PAPS generation in detoxification and bioactivation of xenobiotics in skin is discussed.

摘要

开发了一种快速灵敏的放射性测定法，用于测量大鼠皮肤提取物中3'-磷酸腺苷-5'-磷酸硫酸酯（PAPS）的生物合成。通过大鼠肝脏米诺地尔硫酸转移酶（MST）将35硫酸根转移到米诺地尔上，对35硫酸钠和ATP生成PAP35S的过程进行定量。该测定法灵敏度足以检测低至2 pmol的PAP35S。PAPS生成系统的最适pH为8.6，ATP-Mg2+复合物的表观Km值为1 mM，35硫酸钠的表观Km值为68 microM。单独或以等摩尔浓度共同存在的ATP和Mg2+，在浓度高于8 mM时具有抑制作用。过量（或游离）ATP是ATP-Mg2+复合物的竞争性抑制剂；测得的表观Ki为0.32 mM。在大鼠皮肤胞质溶胶中测得的PAPS生成系统的比活性为0.15 nmol PAPS/分钟/毫克蛋白质。讨论了PAPS生成在皮肤中外源化合物解毒和生物活化中的重要性。