Structural identity of the subunits of pigeon liver malic enzyme

Abstract

Pigeon liver malic enzyme was found to have arginine, alanine, and tyrosine as the only N-terminal, N-1, and N-2 amino acids, respectively. Hydrolysis of the reduced and carboxymethylated malic enzyme by carboxypeptidase A yielded quantitative evidence for the following C-terminal sequence: -Leu-(Phe-Ala)-Ile-Leu-COOH. Fifty-five trypsin-digested peptides were separated by HPLC, in accordance with the arginine and lysine contents of each subunit. This more direct structural evidence strongly supports the conclusion that pigeon liver malic enzyme is composed of four chemically identical subunits.