Chemical characterization of adrenocorticotropin and a novel peptide biosynthesized from a pituitary adenoma of a patient with Cushing's disease

ACTH and another unidentified peptide have been biosynthesized in vitro and purified from a pituitary adenoma of a patient with Cushing's disease. The new peptide had an apparent molecular weightof 4000 daltons and was more acidic than ACTH as analyzed by sodium dodecyl sulfate/urea and acidic (pH 4.5) polyacrylamide gel electrophoreses, respectively. Sequence studies revealed the presence of [35S]methionine at position 3 of the new peptide. High performance liquid chromatographic analysis of [35S]methionine-labeled tryptic fragments of the peptide revealed that this peptide contained gamma MSH- (1-7) within its sequence. Our observations raise the possibility that this peptide contains at its N-terminus gamma MSH, a putative peptide proposed by Nakanishi et al.