Identification of alpha-carboxamidated and carboxy-terminal glycine forms of peptides in bovine hypothalamus, bovine pituitary and porcine heart extracts

Abstract

Two chemical assays have been developed for identifying and quantifying peptides which either could be biologically active by virtue of their alpha-carboxamidation or could be substrates for peptidylglycine alpha-amidating mono-oxygenase. The first assay is specific for the alpha-carboxamide of peptides. Using bis[trifluoroacetoxy]iodobenzene, the alpha-carboxamide was converted via a Hoffman reaction into a primary amine, which was then quantified by ninhydrin. The second assay is specific for glycine at the carboxy-terminus of a peptide. Glycine at the carboxy-terminus was derivatized to form 2-thiohydantoin, which was then separated and quantified by reverse phase HPLC. These assays were used to detect peptides in HPLC-separated extracts of bovine hypothalamus, bovine anterior lobe pituitary and porcine heart which may be of biological interest.