Protein-kinase-C-related kinases (PRKs) are part of the lipid-regulated protein kinases (PKC) which also include liver PAK & PKN. Human PRK1 and PRK2 share structurally similar catalytic domains, but less similar N-terminal regulatory regions suggesting different regulatory domain functions. PRK1 and PRK2, as well as a third member of this family, PRK3, show distinct patterns of expression in adult tissues. Additionally, the serine-threonine kinase PRK2 can be specifically cleaved by casp