The two recently discovered forms of protein phosphatase 2C, termed 2C1 and 2C2, were digested with CNBr or trypsin, and several peptides corresponding to two regions of the protein were sequenced. These studies revealed close homology between the two enzymes with 49 identities over the 62 residues that could be compared directly. The results establish that protein phosphatases 2C1 and 2C2 are the products of different genes. The C-terminus of protein phosphatase 2C2 has also been identified.