Methylthioadenosine

5'-Methylthioadenosine (MTA) is a naturally occurring sulfur-containing nucleoside present in all mammalian tissues. NITA is produced from S-adenosylinethionine mainly through the polyamine biosynthetic pathway, where it behaves as a powerful inhibitory product. This compound is metabolized solely by MTA-phosphorylase, to yield 5-methylthioribose-1-phosphate and adenine, a crucial step in the methionine and purine salvage pathways, respectively. Abundant evidence has accumulated over time suggesting that MTA can affect cellular processes in many ways. NITA has been shown to influence numerous critical responses of the cell including regulation of gene expression, proliferation, differentiation and apoptosis. Although most of these responses have been observed at the pharmacological level, their specificity makes it tempting to speculate that endogenous NITA could play a regulatory role in the cell. Finally, observations carried out in models of liver damage and cancer demonstrate a therapeutic potential for NITA that deserves further consideration. (C) 2003 Elsevier Ltd. All rights reserved.