Identification of variant forms of the neuroendocrine peptide galanin.

Galanin is a neuroendocrine peptide widely distributed in the central and peripheral nervous systems and in endocrine tissues. Using radioimmunoassays, chromatographic separations, and tandem mass spectrometry, we have identified a series of five variant forms of galanin purified from porcine upper intestine. The modified variants include three beta-aspartyl-shifted forms, an oxidized form containing Trp monooxide, and an N-terminally truncated form. All were found to be C-terminally amidated. At least the beta-aspartyl-shifted forms could be of native occurrence. Mechanistic explanations of the mass spectrometric fragmentation patterns of the different forms are suggested.