small conjugating protein-specific endopeptidase activity

Catalysis of the hydrolysis of peptide bonds between an alpha-carboxyl group and an alpha-amino group within a small protein such as ubiquitin or a ubiquitin-like protein (e.g. APG8, ISG15, NEDD8, SUMO).

Source:http://purl.uniprot.org/go/0070137