Cathepsin E is encoded by the ctse gene, exists in the homodimer forms, belongs to the peptidase A1 family. Cathepsin E high expressed in the stomach, clara cells and alveolar macrophages of lung, brain microglia, spleen and activated B-lymphocytes. Cathepsin E may involve in the processing of antigenic peptides during MHC class II-mediated antigen presentation, play a role in activation-induced lymphocyte depletion in the thymus, and in neuronal degeneration and glial cell activation in the brain.

> 95% as determined by SDS-PAGE.