A high phosphotyrosine phosphatase activity is present in differentiating bovine lens cells.

Activity of phosphotyrosine-protein phosphatases (PTPases) has been investigated in the different cellular regions of bovine eye lens. PTPases were tested in cellular detergent extracts using phospholabelled synthetic peptides and p-nitrophenyl phosphate. We show that a high PTPase activity is only present in cells which undergo differentiation, namely the equatorial epithelium and cortex fiber cells. Since this activity is found to be severely inhibited by a specific inhibitor of receptor-type PTPases, it can be suggested that one or more members of this class of PTPases might play an important role in the lens differentiation process.