Selenium and methionine sulfoxide reduction

Abstract

Methionine sulfoxide reductases (Msrs) are repair enzymes that catalyze the reduction of methionine sulfoxide in both free and protein-based forms back to methionine in a stereospecific manner. Methionine sulfoxide reduction is an important pathway that occurs in most organisms, protects cells against oxidative stress and regulates protein function. This pathway is also implicated in delaying the aging process and progression of neurodegenerative diseases. Selenoprotein Msr forms are found in bacteria, unicellular eukaryotes, and animals, and contain selenocysteine, an essential catalytic residue. Selenoprotein MsrB1 is the main Msr in the liver of mammals and its expression is easily regulated by dietary selenium. This chapter discusses the physiological roles of Msrs with the focus on mammalian MsrA and MsrBs and recent studies involving selenoprotein Msrs.