Muscle and liver pyruvate kinases are closely related: amino acid sequence comparisons.

Previous evidence has shown that the M1 and L pyruvate kinase isozymes differ markedly in kinetic and immunological properties, amino acid compositions and peptide maps. However, the amino acid sequence results we present here for the N-terminal region and for a region of the C domain show that the M1 and L isozymes are very similar. The variable length of the N-terminal sequences also explains the difference in regulation by phosphorylation between the M1 and L isozymes. The M1 isozyme lacks the serine residue that has been shown to be phosphorylated in the L isozyme.