Solid‐phase synthesis of PYLa and isolation of its natural counterpart, PGLa [PYLa‐(4–24)] from skin secretion of Xenopus laevis

Abstract

From the nucleotide of clones isolated from a c[complementary]DNA library constructed from skin of X. laevis, the existence of PYLa, a peptide comprised of 24 amino acids, was predicted. This peptide was synthesized by solid-phase methods and purified to homogeneity with an overall yield of 61%. The synthetic peptide was used as reference substance to search for its natural counterpart in skin secretion of Xenopus. Two peptides were found which were very similar to PYLa except for the absence of the first 3 amino acids. These 21-amino-acid peptides, termed PGLa, can be generated from PYLa by cleavage after the single arginine residue present in the latter. The 2 forms of PGLa differ in their retention time on HPLC [high performance liquid chromatography] but have identical amino acid compositions and terminal sequences. Tryptic hydrolysis of synthetic PYLa after the single arginine yields exclusively PGLa with the shorter retention time on HPLC. The chemical difference between the 2 forms of PGLa is currently not known. The possible biological role of these newly discovered constituents of frog skin secretion is discussed.