A classification used in the MEROPS peptidase database; peptidases that can be grouped on the basis of evolutionary relationship. Each clan is identified by two letters, the first representing the catalytic type of the families included in the clan: Aspartic (A), Cysteine (C), Glutamic (G), Metallo (M), Mixed (P), Serine (S), Threonine (T), Unknown (U). The mixed clan contains families of more than one of the catalytic types. Some clans are divided into subclans where there is evidence of ancient divergence.
Subjects: Medicine and Health.