Cathepsin O (CTSO)

Cathepsin O is a cysteine protease and a member of the cathepsin family and papain superfamily. This proteolytic enzyme is involved in cellular protein degradation and turnover. The recombinant form of this enzyme was shown to degrade synthetic peptides typically used as substrates for cysteine proteinases and its proteolytic activity was abolished by an inhibitor of cyteine proteinase.Furthermore, CTSO proteolytic activity was abolished by an inhibitor of this subclass of proteolytic enzymes. Northern blot analysis of polyadenylated RNAs isolated from a variety of human tissues demonstrated that cathepsin O is expressed in all examined tissues, which is consistent with a putative role of this protein as a proteolytic enzyme involved in normal cellular protein degradation and turnover.