Human Legumain/Asparaginyl Endopeptidase Alexa Fluor™ Plus 680-conjugated Antibody

Legumain is a lysosomal cysteine protease whose activity is found in several tissues tested (1, 2). Legumain plays a pivotal role in the endosomal/lysosomal degradation system because the Legumain deficiency causes the accumulation of pro cathepsins B, H and L, another group of lysosomal cysteine proteases (3). Over-expression of Legumain in tumors is significant for invasion/metastasis (4). Also known as Asparaginyl Endopeptidase, it specifically cleaves peptide bonds with Asn at the P1 position. Nevertheless, it also cleaves peptide bonds with Asp at the P1 position. Auto-activation of pro Legumain involves both types of the cleavage, which result in the removal of the pro peptides in both C- and N-termini (5). In addition, Legumain activates pro MMP-2 and processes bacterial antigens for MHC class II presentation and pro thymosin alpha to thymosin alpha₁ and thymosin alpha₁₁, two acidic peptides with immunoregulatory properties (6‑8). Human Legumain is synthesized as a 433 amino acid precursor with a signal peptide (residues 1‑17). The pro enzyme (residues 18‑433) was expressed with an N-terminal His tag. This activity of Legumain can be inhibited by rhCystatins C and E/M and recombinant mouse Cystatin C (R&D Systems, Catalog # 1196-PI, 1286-PI and 1238-PI, respectively).