In spite of biochemical characterization of normal and cataract lenses and decades of research, the etiology of cataract is not clearly understood. The past investigations have shown the occurrence of proteolysis in aged and cataract lenses. However, the proteolytic enzymes identified by their ability to hydrolyze chromogenic, fluorescence or protein substrates have thus far provided only limited insight to the in vivo cleavage mechanisms of alpha-, beta- and gamma-crystallins. We hypothesize that novel proteases, which recognize a specific peptide sequence or tertiary structure around the cleavage site, are responsible for some of the crystallin cleavages occurring during aging and cataract development. We propose to continue our studies on proteolysis in lens with following specific aims. 1) Determine if the in vivo cleavages seen during the characterization of alpha-, beta- and gamma-crystallins from aging and cataract lenses are due to sequence specific proteases. Additionally, to evaluate whether non-enzymatic cleavages are also important mechanisms for the generation of truncated crystallins in vivo, we intend to study the susceptibility of peptides containing in vivo cleavage site sequences to proteolysis by free radical generating systems. 2) Purification and characterization of novel sequence specific proteases identified in lens. 3) Continue the studies on lens acylaminopeptidase, and evaluate its role in the proteolysis of crystallins in vivo. We also hypothesize that the crystallin fragments may play a decisive role in cataractogenesis by interfering in the chaperone activity of alpha-crystallin in vivo. Therefore we propose to continue to studies on the low molecular weight crystallin fragments from lens to investigate their origin and properties including interaction with purified alpha-, beta- and gamma- crystallins.