C-terminal processing peptidase (
EC3.4.21.102, CtpA gene product (Synechocystis sp.), photosystem II D1 protein processing peptidase, protease Re, tail-specific protease, Tsp protease) is an
enzyme.[1][2][3] This enzyme
catalyses the following
chemical reaction
The enzyme shows specific recognition of a
C-terminal tripeptide, Xaa-Yaa-Zaa, in which Xaa is preferably
Ala or
Leu, Yaa is preferably Ala or
Tyr, and Zaa is preferably Ala, but then cleaves at a variable distance from the C-terminus. A typical cleavage is -Ala-Ala!Arg-Ala-Ala-Lys-Glu-Asn-Tyr-Ala-Leu-Ala-Ala. In the
plantchloroplast, the enzyme removes the C-terminal extension of the X1 polypeptide of
photosystem II
Proteolytic processing of the X1 protein of photosystem II enables light-driven assembly of the tetranuclear
manganese cluster.