Cathepsin E

Cathepsin E is an enzyme (EC 3.4.23.34) that in humans is encoded by the CTSE gene. The enzyme is also known as slow-moving proteinase, erythrocyte membrane aspartic proteinase, SMP, EMAP, non-pepsin proteinase, cathepsin D-like acid proteinase, cathepsin E-like acid proteinase, cathepsin D-type proteinase) is an enzyme.

Cathepsin E is a protease found in animals, as well as various other organisms, that belongs to the aspartic protease group. In humans it is encoded by the CTSE gene located at 1q32 on chromosome 1. It is an intracellular non-lysosomal glycoprotein that is mainly found in the skin and in immune cells. The protein is an aspartyl protease that functions as a disulfide-linked homodimer, and has an oligosaccharide chain of the high-mannose type. It is a member of the peptidase A1 family, and therefore observes specificity similar to that of Pepsin A and Cathepsin D. Cathepsin E is an intracellular enzyme and does not appear to be involved in dietary protein digestion. It is found at highest abundance on the stomach’s epithelial mucus producing cell surfaces. It is the first aspartic protease present in the fetal stomach and is found in more than half of gastric cancers, leading to it appearing to be an oncofetal antigen. Transcript variants utilizing alternative polyadenylation signals and two transcript variants encoding different isoforms exist for this gene.

A deficiency in the levels of Cathepsin E in the body may play a part in inflammatory skin diseases such as atopic dermatitis, for which treatment would rely on fixing functionality and levels of the protein in the body. Along with renin and Cathepsin D, Cathepsin E is one of the only few aspartic proteases known to be made in human tissues other than those of gastrointestinal and reproductive tracts.