Abstract
Most amphibians can adapt their colour to that of their background by a mechanism which is controlled by melanophore stimulating hormone (MSH), a product of the pars intermedia of the pituitary gland1. Although the melanotropic peptides of amphibians have never been sequenced, immunological evidence indicates that at least some of them are structurally related to α-MSH2–4. In our studies of the biosynthesis and structure of melanotropic peptides in the pars intermedia of Xenopus laevis, we have found evidence, reported here, for des-Nα-acetyl-α-MSH as the immediate precursor of α-MSH, with the acetylation taking place just before or during release from the pituitary.
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