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C-terminal prodomain of legumain This family contains the C-terminal propeptide of legumain, a lysosomal endopeptidase with a specificity for hydrolysis of asparaginyl bonds. Legumain (also called vacuolar processing enzyme or VPE in plants, and asparaginyl endopeptidase or AEP in animals) is synthesized as a precursor with both N- and C-terminal propeptides. Prolegumain is directed to the lysosome or plant vacuole, where activation occurs at least partially by autolysis. The N-terminal catalytic domain is a cysteine protease from the C13 family. The C-terminal prodomain can be organized into an activation peptide (AP), spanning a helical region, and a C-terminal death domain-like fold, denoted as legumain stabilization and activity modulation (LSAM) domain. The C-terminal prodomain binds over the active site and inhibits the catalytic domain. During activation, the C-terminal prodomain is autocatalytically cleaved. This process is induced by pH changes. Human legumain has been shown to process the tetanus toxin generating the fragments found in class II antigen presentation. Legumain from plant seeds is thought to be responsible for the post-translational processing of seed proteins prior to storage. Legumain is highly expressed in some cancers such as colorectal cancer (CRC) and uveal melanoma (UM); it is associated with poor outcome in CRC and upregulation of legumain is associated with malignant behavior of UM. Thus, legumain may be used as a negative prognostic factor as well as a therapeutic target. |
Lu S et al.(2020). "CDD/SPARCLE: the conserved domain database in 2020.",