| Type: | Family | Name: | Peptidase C1A, placentally-expressed cathepsin |
| Description: | Cysteine peptidases have characteristic molecular topologies, which can be seen not only in their three-dimensional structures, but commonly also in the two-dimensional structures. These are peptidases in which the nucleophile is the sulphydryl group of a cysteine residue. Cysteine proteases are divided into clans (proteins which are evolutionary related), and further sub-divided into families, on the basis of the architecture of their catalytic dyad or triad []. This group of cysteine peptidases belong to the MEROPS peptidase family C1, sub-family C1A (papain family, clan CA).These are lysosomal cysteine-peptidases, characterised by a catalytic triad that includes an active-site cysteine residue [] and a characteristic ER(F/W)NIN motif within the propeptide indicating that these protease belongs to the cathepsin L-like sub-group [].Species and strain variants of a family of placentally expressed cathepsins (PECs) were cloned and sequenced in order to identify evolutionary conserved structural characteristics of this large family of cysteine proteases []. Cathepsins M, P, Q, and R, are conserved in mice and rats but homologues of these genes are not found in human or rabbit placenta, showing that this group of proteases are probably restricted to rodents. Species-specific gene duplications have given rise to variants of cathepsin M in mice, and cathepsin Q in rats. Although the PECs have diverged at a greater rate than the other lysosomal cathepsins, residues around the specificity sub-sites of the individual enzymes are conserved. Strain-specific polymorphisms show that the evolutionary rate of divergence of cathepsins M and 3, the most recently duplicated pair of mouse genes, is even higher than the other PECs. In human placenta, critical functions of the PECs are probably performed by broader specificity proteases such as cathepsin L. | Short Name: | Pept_C1A_placental-cathepsin |
