Post-translational modifications of pro-opiomelanocrtin related hormones in medaka pituitary based on mass spectrometric analyses.

Direct tissue matrix-assisted laser desorption ionization with time-of-flight mass spectrometry analysis provides a selective detection of mass profile for the peptides contained into cell secretory granules. By this mass spectrometry with slice of pituitary, two novel molecular forms of pro-opimelanocrtin related hormone were found in the orange-red strain medaka (Oryzias latipes var.). The structures of [N,O-diacetyl Serine(1), O-acetyl Serine(3)]-α-melanocyte-stimulating hormone (MSH) and [hydroxyproline(15)]-β-MSH, together with [phosphoserine(15)]-corticotropin-like intermediate lobe peptide, were determined for the first time using a collision-induced dissociation with electrospray ionization mass spectrometry. A combination of mass spectrometry analyses is thus a powerful tool to lead to the elucidation of the post-translational processing from the pre-prohormone.