Legumain (EC 3.4.22.34)

Abstract It has been known since the initial discovery of Csoma and Polgar in 1984 [1292] that the seeds of several legumes and other plants contain an endopeptidase specific for the hydrolysis of asparaginyl bonds. The enzyme has been termed asparagi!!JI endopeptidase [1259] and vacuolar processing enzyme [1305], but the name recommended by the nomenclature committee of the IUBMB is legumain. Kembhavi et al. [1389] in 1993 isolated legumain from moth bean (Vigna aconitifo!ia) and described a convenient fluorimetric assay in which the substrate was Z-Ala-Ala-Asn-NHMec. The cloning and sequencing of legumain from castor bean [1381] revealed some sequence identities with the 'haemoglobinase', from the blood fluke, Schistosoma mansoni. The parasite enzyme has now been shown also to be an asparaginyl endopeptidase and termed Schistosoma legumain [1638]. In reviewing the cysteine peptidases, Rawlings and Barrett [1187] assigned the number Cl 3 to the peptidase family containing the legume asparaginyl endopeptidase and the Schistosoma endopeptidase. This family shows no relationship to the papain family, Cl, to which all the other lysosomal cysteine proteinases belong. During 1995, the publication of human EST sequences made it clear that the human genome contains a form of legumain. This prompted Barrett and co-workers in 1997 [1783] to clone and sequence the cDNA for human legumain and to isolate and characterize the enzyme from pig kidney, using the assay that they had introduced earlier for the moth bean enzyme. The properties of the mammalian enzyme were so similar to those of the plant and Schistosoma forms that it seems appropriate to retain the same name, leJ,umain, for the mammalian enzyme.