A growing body of evidence relates selenium to cancer prevention, immune system function, male fertility, cardiovascular disorder, control of the aging and neurodiseases process. Selenoproteins are thought to be responsible for the majority of these biomedical effects of selenium. Approximately 17 selenoproteins have been identified until now. Although the function of many selenoproteins are unknown, some play important roles in antioxidant mechanisms. It has been also implicated in the regulation of signaling pathways through catalysis of thiol/ disulfide exchange. Selenoprotein M(SelM) is especially expressed in a mammalian brain and is localized to the perinuclear structures (Golgi/ER). The roles of selM have not been clearly identified until present time.