, other forms of classification can be proposed that consider
their chemical structures and thus contain information about
their evolutionary families, such as MEROPS databases (peptidase
database) [24–26]. Considering, principally, the tertiary structure
of the protein and its catalytic sites, proteases can be classified in
clans, and clans divided in families. Every clan provides information
about the catalytic structure of the proteases. The names take into
account the iconic amino acid or metal present in the active site:
Aspartic peptidases (A), Cysteine peptidases (C), Metallo peptidases
(M), Serine peptidases (S), Mixed catalytic type (P) and Unknown
type (U)