<prompt> Selenium is a cofactor in following enzymeGlutathione peroxidaseCytochrome oxidaseCytochrome reductaseXanthine oxidase  <response>: Selenium21st amino acid Selenocysteine RDA 50 - 100 mcgdaySelenium as a co-factorSelenium deficiencySelenium toxicityGlutathione peroxidaseDeiodinase Thioredoxin reductase Keshans cardiomegaly Kashin-beck disease Peripheral neuropathy Garlic odor to breathDermatitis Refer: DM Vasudevan, Textbook of Biochemistry, 7th edition, pg no: 523 