The selenoprotein phospholipid hydroperoxide glutathione peroxidase (PHGPx)
changes its physical characteristics and biological functions during sperm
maturation. PHGPx exists as a Soluble peroxidase in spermatids but persist
s in mature spermatozoa as an enzymatically inactive, oxidatively cross-lin
ked, insoluble protein. in the midpiece of mature spermatozoa, PHGPx protei
n represents at least 50 percent of the capsule material that embeds the he
lix of mitochondria. The role of PHGPx as a structural protein may explain
the mechanical instability of the mitochondrial midpiece that is observed i
n selenium deficiency.