A cDNA encoding M2-type pyruvate kinase from mouse was cloned and its nucleotide sequence was determined. The cDNA encoded a protein containing 531 amino acids, the nucleotide and amino acid sequences of which were 93.2% and 98.1%, respectively, homologous to those of rat M2 pyruvate kinase. Expression of the pyruvate kinase in mouse embryonal carcinoma P19 cells altered according to differentiation stages; high at undifferentiated and low at differentiated stages.