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  • Title: The role of 5'-methylthioadenosine phosphorylase in 5'-methylthioadenosine-mediated inhibition of lymphocyte transformation.
    Author: Ferro AJ, Vandenbark AA, Marchitto K.
    Journal: Biochim Biophys Acta; 1979 Dec 11; 588(3):294-301. PubMed ID: 116688.
    Abstract:
    To determine if increased 5'-methylthioadenosine phosphorylase activity in activated lymphocytes may be responsible for the decreased inhibitory effect noted when 5'-methylthioadenosine is added after stimulation, the activity of this enzyme was monitored during lymphocyte transformation. A direct correlation existed between the transformation process and 5'-methylthioadenosine phosphorylase activity; the longer the stimulation process progressed, the phosphorylase activity; the longer the stimulation process progressed, the greater the enzyme activity. The 7-deaza analog of 5'-methylthioadenosine, 5'-methylthiotubercidin, was utilized to explore further the role that the phosphorylase may play in the reversal process. 5'-Methylthiotubercidin acted as a potent inhibitor, but not a substrate, of the 5'-methylthioadenosine phosphorylase, and was an even more potent inhibitor of lymphocyte transformation than 5'-methylthioadenosine. However, in direct contrast to the 5'-methylthioadenosine effect, inhibition by 5'-methylthiotubercidin could not be completely reversed. These data suggest the 5'-methylthioadenosine phosphorylase plays an important role in reversing 5'-methylthioadenosine-mediated inhibition and that the potent, nonreversible inhibitory effects of 5'-methylthiotubercidin are due to its resistance to 5'-methylthioadenosine phosphorylase degradation.
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