Glutathione peroxidase which protect erythrocytes against hemolysis contain the following element:

In red blood cells, the pentose phosphate pathway is the sole source of NADPH for the reduction of oxidized glutathione. Reduced glutathione removes H2O2 in a reaction catalyzed by glutathione peroxidase, an enzyme that contains the selenium analog of cysteine (selenocysteine) at the active site. The reaction is impoant since accumulation of H2O2 may decrease the lifespan of the erythrocyte by causing oxidative damage to the cell membrane, leading to hemolysis. Ref: Bender D.A., Mayes P.A. (2011). Chapter 21. The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.