Identification of a novel protein phosphatase catalytic subunit by cDNA cloning

A cDNA encoding a novel protein phosphatase catalytic subunit (protein phosphatase X) has been isolated from a rabbit liver library. It codes for a protein having 45% and 65% amino acid sequence identity, respectively, to the catalytic subunits of protein phosphatase 1 and protein phosphatase 2A from skeletal muscle. The enzyme is neither the hepatic form of protein phosphatase 1 or 2A, nor is it protein phosphatase 2B or 2C. The possible identity of protein phosphatase X is discussed.