Ubiquitin carboxyl-terminal hydrolases (EC 184.108.40.206) (UCH) (deubiquitinating
enzymes) [1,2] are thiol proteases that recognize and hydrolyze the peptide
bond at the C-terminal glycine of ubiquitin. These enzymes are involved in the
processing of poly-ubiquitin precursors as well as that of ubiquinated
There are two distinct families of UCH. The first class consist of enzymes of
about 25 Kd and is currently represented by:
Mammalian isozymes L1, L3 and L5.
One of the active site residues of class-I UCH  is a cysteine. We derived
a signature pattern from the region around that residue.
These proteins belong to family C12 in the classification of peptidases
December 2001 / Text revised.
PROSITE method (with tools and information) covered by this documentation:
PROSITE is copyright. It is produced by the SIB Swiss Institute
Bioinformatics. There are no restrictions on its use by non-profit
institutions as long as its content is in no way modified. Usage by and
for commercial entities requires a license agreement. For information
about the licensing scheme send an email to
or see: prosite_license.html.