Transglutaminase activity has been detected in the lenses of laboratory animals and in human cataracts. However, its distribution in the lens tissue has not been investigated. Using a monoclonal antibody against tissue transglutaminase, we showed by Western blotting and immunoabsorption that transglutaminase of normal human lens is immunologically related to tissue transglutaminase but has a slightly higher M(r) than the latter enzyme. Using monoclonal or polyclonal antibody against tissue transglutaminase, lens transglutaminase was localized to the epithelial cell layer on the anterior lens surface and to a thin stripe between the capsule and the peripheral cortex on the posterior surface. Lens fibers were not stained with the antibodies. Factor XIII, another transglutaminase, could not be detected in the lens tissue. The localization of transglutaminase in the lens suggests that lens transglutaminase is synthesized in the epithelial cells and secreted into the virtual space between the capsule and the peripheral cortex spreading all around the lens substance.
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