Goldfish calcitonin: purification, characterization, and hypocalcemic potency.

A novel teleost calcitonin was isolated from the goldfish, Carassius auratus, and its amino acid sequence was determined to be H-Cys-Ser-Ser-Leu-Ser-Thr-Cys-Val-Leu-Gly- Lys-Leu-Ser-Gln-Glu-Leu-His-Lys-Leu-Gln-Thr-Tyr-Pro-Arg-Thr-Asn-Val-Gly- Ala-Gly-Thr-Pro-NH2. The structure of goldfish calcitonin (gCT) was similar to that of salmon calcitonin (sCT) but differed from the latter at positions 3, 27, and 29. The hypocalcemic activity of gCT was estimated to be 3,470 IU/mg by the standardized rat bioassay method, compared with a value of 3,500 IU/mg for sCT. After administration of gCT to young goldfish, the serum Ca concentration was significantly lower in some cases than in controls. However, in other cases no such difference was recognized.