388
N Cys
@ Ser
Asn Leu
D. HAROLD COPP
Cys Val ILeulGly ILyslLeulSer lGln lGlulLeulHis I L y s l L e u F
Thr
Ser
C. Chemistry
Pure calcitonin has been prepared from hog thyroids in a number of
laboratories and its structure has been determined (Bell et al., 1988;
Neher et al., 1968; Potts et al., 1968). The amino acid composition is given
in Table 11, and the structure is shown in Fig. 6. The hormone has been
synthesized by Rittel et aZ. (1968). Porcine calcitonin is a straight chain
peptide containing 32 amino acid residues, with a molecular weight of
approximately 3600. Like vasopressin and oxytocin, it has a disulfide
bridge at the N terminus and an amide at the C terminus. It lacks lysine
and isoleucine.
Copp et al. (1968) and ODor et al. (1969a) observed that the calcitonin activity extracted from salmon ultimobranchials was less retarded
on a standardized Sephadex G-50 column than porcine calcitonin. They
suggested that this might be due to a higher molecular weight (4500).
However, pure salmon calcitonin has now been isolated (Parkes et al.,
1969; ODor et al., 1969b) and has the same number of amino acids (32)
and a lower molecular weight (3427) than the porcine hormone. The
amino acid composition is shown in Table 11. The biological activity of
Fig. 8. ( a ) Structure of salmon calcitonin. From Niall et al. (1969). ( b )
Structure of porcine calcitonin (changed amino acids underlined).