310 CHOH HAO LI [18 



and physicochemical characteristics differ from those described for cortico- 

 tropin-A. In the same year, BelF^ and his colleagues of the American Cyana- 

 mid Company announced the purification of j8-corticotropin from ACTH 

 concentrates of pig pituitaries. Since both the Armour and American Cyana- 

 mid groups employed unhydrolyzed pig ACTH concentrates as their starting 

 material, it cannot be assumed that corticotropin-A and )8-corticotropin are 

 different peptides. The isolation of a polypeptide possessing adrenocortico- 

 tropic activity from bovine pituitaries in pure form has only recently been 

 described. ^^ Physicochemical properties of the bovine hormone are identical 

 in every respect with that of the sheep a-corticotropin. The corticotropins 

 from all three species are made up of 39 amino acids in a single polypeptide 

 chain with serine as the A^-terminal amino acid and phenylalanine at the 

 C-terminus. 



The complete amino acid sequences of the pig corticotropin-A and of 

 the sheep a-corticotropin have been eludicated.^"-*^ Preliminary structural 

 investigations on the beef corticotropin*- indicated that its amino acid 

 sequence is identical with that of the sheep a- ACTH.*" It may be seen in 

 Table 3 that the complete sequence was derived from the identification of 

 over 40 different peptide fragments obtained by chymotryptic, tryptic, peptic 

 and partial acid hydrolysis, as well as by submitting the whole molecule 

 to stepwise degradation by the phenylisothiocyanate (PITC) procedure of 

 Edman and to kinetic investigations with leucine aminopeptidase (LAP) and 

 carboxypeptidase, and from A^- and C-terminal residue analyses by the 

 fluorodinitrobenzene (FDNB) procedure of Sanger and hydrazinolysis ac- 

 cording to the procedure of Akabori, respectively. 



There are two amide groups in sheep a-corticotropin. The location of 

 one of these groups in position 33 was recently established in the course of 

 a kinetic investigation carried out with J. Léonis and D. Chung on the 

 effect of chymotryptic digestion on the hormone peptide. The location of 

 the other amide is yet to be determined, but there have been no indications 

 that it occurs in position 30 as it does in the case of pig corticotropin-A 

 (Cyanamid).*" In this connection, it is of interest to note that pig cortico- 

 tropin-A (Armour) possesses no amides at all.^^ Moreover, there are some 

 variations, reported by three groups of investigators,*" ^^-^^ with respect to 

 the amino acids in positions 25-28, as shown in Table 4. It may be noted 

 that the component amino acids in this segment are the same in all cases; 

 only the order differs. Moreover, the only difference in amino acid composi- 

 tion between the peptide hormones isolated from sheep (beef) and pig glands 

 appears to be one more serine and one less leucine in the former, ^•'-^^ owing 

 to an . . . Ala.Ser . . . sequence in the sheep peptide in place of a . . . Leu. Ala . . . 

 sequence in the pig peptide at amino acid positions 31-32. 



Despite their differences in amino acid composition, and variations in 

 certain portions of their amino acid sequence, both sheep a-corticotropin and 

 pig corticotropin-A possess identical specific ACTH activity. Consequently, 



