PPP5C is the protein phosphatase 5 catalytic unit that is a member of the large PPP family of serine/threonine protein phosphatases. PPP5C plays a role in mediating stress-activated signaling pathways and the DNA damage response. Unlike PP1, PP2A, and PPP4, which function as dimeric or trimeric enzymes, PPP5 functions as a monomer. PPP5 exists as a regulatory N-terminal tetratricopeptide repeat (TPR) domain fused to a C-terminal phosphatase catalytic domain. PPP5C has been demonstrated to associate with and regulate ATM and DNA-PK.