Isolation of human met-enkephalin and two groups of putative precursors (2K-pro-met-enkephalin) from an adrenal medullary tumour

Human met-enkephalin from an adrenal medullary tumour has been purified and characterised. Two groups of putative human met-enkephalin precursors (MW ～ 2000) were also isolated and were only opiate active after trypsinisation and yielded met-enkephalin on further treatment with carboxypeptidase B. Amino acid analyses of these peptides show they are not related to β-LPH nor any other reported putative enkephalin precursors. Their amino acid compositions suggest they are structurally closely related and may represent two groups of heterologous peptides.