Yang Y S, Tsai S W, Lin E S
Institute of Biological Science and Technology, College of Science, National Chiao Tung University, Hsinchu, Taiwan, ROC.
Chem Biol Interact. 1998 Feb 20;109(1-3):129-35. doi: 10.1016/s0009-2797(97)00127-0.
Known spectroscopic and kinetic data are used to formulate pathways of the physiological and transfer reactions and the substrate inhibition of phenol sulfotransferase. Kinetic mechanisms indicate that release of PAP from enzyme complex is required for the physiological reaction but not for the transfer reaction. The pathways explain rate difference between the physiological and transfer reactions since the release of PAP is the rate-limiting step of the former reaction. Two enzyme species of phenol sulfotransferase which distinguish the physiological and transfer reaction were found to involve the binding of PAP. Differences between two forms of phenol sulfotransferase, alpha and beta, indicate that they assemble through different folding process. It is demonstrated that only alpha enzyme renatures in the presence of PAP and beta enzyme renatures only in the absence of PAP in vitro. In the over-expressed system, formation of alpha and beta phenol sulfotransferase is also dependent on the availability of PAP in Escherichia coli. It is concluded that folding of phenol sulfotransferase is assisted by PAP to form alpha enzyme. In the absence of PAP, beta form of phenol sulfotransferase is produced.
已知的光谱和动力学数据被用于阐述生理反应、转移反应以及酚磺基转移酶的底物抑制作用的途径。动力学机制表明，从酶复合物中释放磷酸腺苷磷酸（PAP）对于生理反应是必需的，但对于转移反应则不是。这些途径解释了生理反应和转移反应之间的速率差异，因为PAP的释放是前一个反应的限速步骤。已发现区分生理反应和转移反应的两种酚磺基转移酶同工酶涉及PAP的结合。酚磺基转移酶的α和β两种形式之间的差异表明，它们通过不同的折叠过程组装。结果表明，在体外，只有α酶在PAP存在时复性，而β酶仅在无PAP时复性。在过表达系统中，α和β酚磺基转移酶的形成也取决于大肠杆菌中PAP的可用性。得出的结论是，PAP辅助酚磺基转移酶折叠以形成α酶。在没有PAP的情况下，会产生β形式的酚磺基转移酶。
