Approach to studying proteinase specificity by continuous-flow fast atom bombardment mass spectrometry and high-performance liquid chromatography combined with photodiode-array ultraviolet detection.

Fast atom bombardment mass spectrometry (FAB-MS) and high-performance liquid chromatography using a photodiode-array ultraviolet detector were applied to study a dynorphin-converting endopeptidase from the human pituitary gland. The specificity of the enzyme was tested towards various opioid peptides derived from the prodynorphin precursor, i.e. dynorphin A, dynorphin B and alpha-neoendorphin. Peptide fragments were analysed directly by continuous-flow FAB-MS and those containing aromatic amino acids were detected independently by the photodiode-array ultraviolet detector. The results obtained suggest a similar processing of these structure-related substrates and it appears that the enzyme recognizes the dibasic stretch in their sequence. It is also clear from this study that the combination of the above techniques provides a powerful tool for studies of enzymatic conversion among the prodynorphin-derived peptides and it should be applicable to studies of similar mechanisms in other peptide systems.