The primary structure of a teleost prepro-urotensin II may be deduced from the nucleotide sequence of cloned DNA complementary to carp prepro-urotensin II mRNA but the pathway of post-translational processing of the precursor is unknown. In this study, we have isolated four peptides from an extract of flounder urophysis that are derived from prepro-urotensin II by proteolytic cleavage. The amino acid sequences of the peptides demonstrate that flounder prepro-urotensin II is cleaved at two monobasic processing sites (single arginine residues) to generate peptides with limited homology to carp prepro-urotensin II-(22–4l)-, -(42–87)- and -(88–110)-peptides. Cleavage at a tribasic residue processing site generates a urotensin II with the primary structure: Ala-Gly-Thr-Thr-Glu-Cys-Phe-Trp-Lys-Tyr-Cys-Val. Urotensin II-(4–12)-peptide represented a minor component in the extract.
