| Summary: | 碩士 === 國立交通大學 === 生物科技研究所 === 89 === Phenol sulfotransferase (PST) catalyzes sulfuryl group transfer from adenosine 3’-phosphate 5’-phosphosulfate (PAPS) to a variety of nucleophilic acceptor in biological system. Although several PSTs have been purified and examined by steady state kinetic methods, little is known about ligands binding and conformational change in these enzymes. In the present study, we investigated conformational change of PST induced by ligands and environmental change of ligands binding site using UV/visible absorption, circular dichroism, and fluorescence techniques. Our experimental data show that the ratio of PST (dimer)：adenosine 3’,5’-bisphosphate (PAP)：p-nitrophenol (pNP) is 1：1：1, determined through the change of an unique pNP absorption maximum at 375 nm. The result suggests that binding ability of two subunits of PST is significantly different. Different nucleotides, such as adenosine 5’-monophosphate (AMP) or adenosine 3’-monophosphate (3’-AMP), are also tightly bound to PST. Unlike PAP, they do not induce the same spectral change observed with PAP binding. The effects of these nucleotides on the conformational change of PST are indicated by different spectroscopies. Different phenols are used to replace p-NP and, similar to that of p-NP, their spectral differences are observed in the presence of PAP. The result suggests that the phenolic compounds become deprotonated as they get into the active site of PST. Mechanism and inhibition of sulfuryl group transfer catalyzed by PST are proposed base on the above studies.
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