ZDHHC9 is a palmitoyl acyltransferase (PAT) whose substrates include small GTPases, such as H-Ras, N-Ras and R-Ras [, ], Lck kinase, and many transmembrane proteins and channels []. Mutations in ZDHHC9 cause mental retardation, X-linked, syndromic, ZDHHC9-related (MRXSZ) [].