Aconitase has been purified from membranes prepared from both the human gastric carcinoma cell line Okajima and from porcine gastric mucosa by chromatography on concanavalin A-Sepharose and carboxymethyl-Sepharose, and preparative polyacrylamide gel electrophoresis. Automated Edman degradation of the intact proteins yielded no N-terminal amino acid sequence due, presumably, to N-terminal blockage. Sequence analysis of tryptic peptides derived from S-carboxymethyl porcine and human aconitases established the positions of 95 and 64 amino acid residues, respectively. The amino acid sequence data for porcine aconitase was in perfect agreement with the previously reported cDNA-deduced amino acid sequence [Zheng et al. (1990) J Biol Chem 265:2814-2821]. Comparison of the human amino acid sequence data with the cDNA-deduced amino acid sequence of porcine aconitase indicated that these two proteins have 95% amino acid sequence identity within the sequenced region.