Cathepsin E (CTSE) Antibody – Mouse Monoclonal

The protein encoded by this gene is a gastric aspartyl protease that functions as a disulfide-linked homodimer. This protease, which is a member of the peptidase C1 family, has a specificity similar to that of pepsin A and cathepsin D. It is an intracellular proteinase that does not appear to be involved in the digestion of dietary protein and is found in highest concentration in the surface of epithelial mucus-producing cells of the stomach. It is the first aspartic proteinase expressed in the fetal stomach and is found in more than half of gastric cancers. It appears, therefore, to be an oncofetal antigen. Transcript variants utilizing alternative polyadenylation signals and two transcript variants encoding different isoforms exist for this gene. [provided by RefSeq, Jul 2008]

Function: May have a role in immune function. Probably involved in the processing of antigenic peptides during MHC class II-mediated antigen presentation. May play a role in activation-induced lymphocyte depletion in the thymus, and in neuronal degeneration and glial cell activation in the brain. Ref.12

Catalytic activity: Similar to cathepsin D, but slightly broader specificity. Ref.11 Ref.12

Subunit structure: Homodimer; disulfide-linked. Ref.11

Subcellular location: Endosome. Note: The proenzyme is localized to the endoplasmic reticulum and Golgi apparatus, while the mature enzyme is localized to the endosome. Ref.3

Tissue specificity: Expressed abundantly in the stomach, the Clara cells of the lung and activated B-lymphocytes, and at lower levels in lymph nodes, skin and spleen. Not expressed in resting B-lymphocytes. Ref.2 Ref.12 Ref.13

Post-translational modification: Glycosylated. The nature of the carbohydrate chain varies between cell types. In fibroblasts, the proenzyme contains a high mannose-type oligosaccharide, while the mature enzyme contains a complex-type oligosaccharide. In erythrocyte membranes, both the proenzyme and mature enzyme contain a complex-type oligosaccharide. Ref.3 Ref.9 Ref.10Two forms are produced by autocatalytic cleavage, form I begins at Ile-54, form II begins at Thr-57.

Sequence similarities: Belongs to the peptidase A1 family.

Biophysicochemical propertiesKinetic parameters:KM=0.06 mM for hemoglobin Ref.9KM=0.13 mM for Pro-Pro-Thr-Ile-Phe-Phe(4-NO2)-Arg-LeuKM=0.04 mM for Lys-Pro-Ile-Glu-Phe-Phe(4-NO2)-Arg-Leu