The Enzymatic Antioxidant System of Human Spermatozoa
Figure 4
Fate of 2-Cys PRDXs when scavenging ROS. 2-Cys PRDXs react with H2O2 and become oxidized and therefore inactive. The TRX/TRD can reduce PRDXs in order to allow another cycle of scavenging of ROS. To assure proper function of this system, glucose-6-P dehydrogenase (G6PDH) and/or NADP-dependent isocitrate dehydrogenase (NADP-ICDH) supply enough reducing equivalent in the form of NADPH. If there is a strong oxidative stress (with high amounts of intracellular H2O2, for example), 2-Cys PRDXs are sulfonated and inactive. This inactivation cannot be reversed by the TRX/TRD system and 2-Cys-PRDXs can only be reactivated by sulfiredoxin (SRX) or sestrin 1 (SESN1) and donors of thiol groups (-SH) like reduced glutathione.
