Primary structure of bovine adrenal phenylethanolamine N-methyltransferase

Bovine adrenal medullary phenylethanolamine N-methyltransferase (E.C. 2.1.1.28) was sequenced to determine if primary structure or post-translational processing accounts for the charged isozymes. A blocked NH2-terminus precluded amino terminal sequencing. Therefore, cyanogen bromide and tryptic peptide fragments were isolated and subjected to gas phase/gas-liquid phase sequencing. Primary structure was identified for 45% of the protein. At least two polypeptide chains exist with alternative amino acids representing conservative changes or single-base changes in amino acid codons by comparison to the cDNA sequence for the enzyme.