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18] STRUCTURE OF PITUITARY HORMONES 325 



of a branched polypeptide chain having two A^-terminal residues (phenyla- 

 lanine and alanine) and only one C-terminal residue (phenylalanine), whereas 

 whale, monkey and human somatotropins are made up of only one poly- 

 peptide chain with phenylalanine as both the A^-terminal and the C-terminal 

 residues. As is evident from Table 12, somatotropins isolated from pituitary 

 glands of various species can easily be differentiated by the A^- and C-terminal 



Table 11 



SOME PHYSICOCHEMICAL PROPERTIES OF VARIOUS 

 SOMATOTROPINS 



* S20, w^ S\ D20, to in cm^/sec.; V in cc./g.; f/fo, dissymmetry constant; Pi, isoelectric 

 point; cystine in residues per mole. 



Table 12 



N- AND C-TERMINAL SEQUENCES OF 

 SOMATOTROPINS FROM VARIOUS SPECIES 



• By the phenylisothiocarbamyl procedure of Edman; the quantitative estimates of the 

 A^-terminal residue were obtained by Sanger's fluorodinitrobenzene procedure. 



t As revealed by the action of carboxypeptidase; the C-terminal residue was verified 

 by the hydrazinolysis procedure of Akabori. 



t A^-terminal amino acid sequences were established by identification of DNP-peptides 

 in partial acid hydroly sates of the bovine DNP-somato tropin. 



