The PPPDE superfamily (after Permuted Papain fold Peptidases of DsRNA viruses and Eukaryotes), consists of predicted thiol peptidases with a circularly permuted papain-like fold. The inference of the likely DUB function of the PPPDE superfamily proteins is based on the fusions of the catalytic domain to Ub-binding PUG (PUB)/UBA domains and a novel alpha-helical Ub-associated domain (the PUL domain, after PLAP, Ufd3p and Lub1p) [1].

1: Novel predicted peptidases with a potential role in the ubiquitin signaling pathway. Iyer LM, Koonin EV, Aravind L; Cell Cycle 2004;3:1440-1450. PMID:15483401