Amino terminal sequence analysis of human placenta aromatase

The amino acid composition and the amino-terminal amino acid sequence from position 1 to 21 of human placenta aromatase were determined. In addition, a cysteine containing peptide with a sequence homologous to those of peptides containing the cysteine residue which was suggested to provide the proximal thiolate ligand to the heme in other cytochrome p-450 isozymes, was identified. The results indicate that aromatase is a cytochrome p-450 protein, probably derived from a new cytochrome p-450 family.