Amino acid sequence of 37 residues surrounding Nxi-pyridoxyllysine in mitochondrial aspartate aminotransferase.

Following reduction with NaBH4, carboxymethylation and cleavage with cyanogen bromide, a peptide of thirty-seven amino acid residues containing N^?-pyridoxyllysine (coenzyme binding lysine) was isolated from the mitochondrial aspartate aminotransferase of pig heart by Sephadex G-75 column chromatography and then preparative polyacrylamide gel electrophoresis. The primary structure of this peptide was determined to be Ala-Tyr-Gln-Gly-Phe-Ala-Ser-Gly-Asp-Gly-Asn-Lys-Asp-Ala-Trp-Ala-Val-Arg-His-Phe-Ile-Glu-Gln-Gly-Ile-Asn-Val-Cys-Leu-Cys-Gln-Ser-Tyr-Ala-(Pxy) Lys-Asn-Met. Its structure showed a high degree of homology with the corresponding part of the cytoplasmic isozyme.