Legumain (LGMN)

Legumain is a cysteine protease enzyme encoded by the LGMN gene, predominantly localized to the endolysosomal system where it cleaves peptide bonds specifically after asparagine residues, a unique proteolytic specificity that has earned it the synonym "Asparaginyl endopeptidase (AEP)"[2][7][4]. It is synthesized as an inactive zymogen and becomes activated via acidic pH-induced autocatalysis during endosome/lysosome maturation. Legumain plays a central role in antigen processing for MHC class II presentation and is crucial for proper immune function. In various solid tumors and aging brain tissue, legumain is often overexpressed and aberrantly localized (including extracellular, nuclear, and cytosolic), where it contributes to tumor progression, metastasis, and potentially neuronal injury[7][4]. Legumain also exhibits pH-dependent peptide ligase activity, expanding its functional repertoire in protein and peptide modification. Owing to its disease association and unique enzymatic properties, legumain is a target of ongoing research for development of diagnostic biomarkers, cancer therapeutics, and molecular imaging probes[7][4][2][1].

Other names

Asparaginyl endopeptidaseLGMNAEPVacuolar processing enzyme

Inhibitors: Block the protease's catalytic cysteine to inhibit asparaginyl hydrolysis, disrupting protein degradation and antigen processing. Imaging/theranostic agents: Covalently bind the active site for diagnostic imaging of tumors overexpressing activated legumain. Prodrugs: Designed to be activated by legumain's enzymatic activity within tumor microenvironments.