Postsynthetic changes of glutathione peroxidase (EC 1.11.1.9) and glutathione reductase (EC 1.6.4.2) in the ageing bovine lens.

Postsynthetic changes in the enzyme and structural proteins play an important role in the mechanisms of ageing of the lens, when development of protein aggregates and -S-S- linking occurs. Protection of the free -SH groups through the glutathione peroxidase and glutathione reductase system is a prerequisite to avoid these phenomena. Investigations on these two enzymes in young and old bovine lens tissues showed that they are themselves subjected to age-dependent modifications. With increasing age, the specific activity decreases while a simultaneous increase in heat lability occurs. This means that in the course of postsynthetic processes the stability of the conformation decreases and that finally the catalytic properties are lost.