IDENTIFICATION OF A MELANOCYTE GROWTH-INHIBITING TRIPEPTIDE AND DETERMINATION OF ITS STRUCTURE

The function and proliferation of melanocyte cell populations are infl uenced by a wide range of hormones and growth factors. Local cell rene wal after sudden melanocyte loss appears to be regulated according to a negative feedback principle, however. In accordance with this assump tion, we have examined growth-inhibitory activity in water extracts of cultured non-transformed melanocytes and melanoma cells (B16 cells). The extracts were fractionated by gel filtration on Sephadex G-25 and Fractogel MG 2000, by ion-exchange chromatography on DEAE-cellulose an d Dowex 50 and by reverse-phase high-performance liquid chromatography on Bondesil and Partisil columns. Two peptides were isolated with the structures pyroGlu-Phe-GlyNH(2) and pyroGlu-Cys-GlyNH(2) as revealed by mass spectrometry, peptide sequencing and amino acid analysis. The two peptides were synthesized and tested for the ability to inhibit th e growth of melanocyte cultures. Only pyroGlu-Phe-GlyNHz was inhibitor y. The dose-response curve was bell-shaped with maximum inhibition aro und 10(-15) M. The melanocyte tripeptide thus appears to be a new memb er of a group of N-substituted growth-regulating oligopeptides found i n other tissues. (C) Munksgaard 1997.