On the Origin of the Fore-protein 



119 





— CH2— o 



CH2 



I 



CH— NH2 



I 

 COOH 



PHjI NH3— Na 



COC12 HCl t \ 



/"VCH^-O 



COat 



CH2 

 I 

 CH— NH 



CO — o 



/" 



CO 



OH 



I 



CH2 

 I 

 -NH— CH— CO— 



w = 37 



CH2 

 I 

 — NH— CH— CO— 



6nHC1 



o-5NNaOH 



*~ 



/'~\— CH2SH 



room temp. 



S-Benzylcysteine 



Hydrolysis 



-^- Serine 



Alam'ne 



Fig. 2. 



5— CHa— O 

 I 

 GHz 



I 

 — NH— CH— CO- 



CH2 

 — NH— C— CO- 



"J 



The formation of aspartyl residue in the fore-protein is also most likely to 

 have occurred by a series of reactions shown in Fig. 3. The experiment to test 

 this possibility was carried out by employing polydehydroalanine synthesized 

 by Sakakibara from carbobenzoxy-dehydroalanine as shown in the figure. 



NH NH NH NH NH 



I CH2O I HCN I I I 



CHa ■ ^ C = CH2 ^ CH— CH2— CN^ CH— CHa- CONH2-> CH— CHa- COOH 



CO 



CO 



CH2 



C— COOH 



CO 



CO 



I AspCNHa). 



CO 



I Asp. 



PCI. 



CHa 



— CO2 



-CO 



Poly-Dehydroalanine 

 CHa 



II 

 C 



/ \ 

 — NH CO—. 



NH- 



-CO— O— CH2— ^ x> NH — CO 



n = 100 



- tl"^^° 



CH2— OH 



I 

 CH 



/ ^ 



— NH.| CO- 



tlCHaO 



Gly. [— NH— CH>— CO— ] „ 



Fig. 3. Formation of aspartic acid. 



olydehydroalanine is a light-brown, amorphous powder, which is soluble in 

 water and formic acid but not in alcohols. This polymer was dissolved in water 

 with potassium cyanide and kept at 20-25° for 20 hours in a sealed tube and 

 then hydrolysed by hydrochloric acid. The hydrolysate was chromatographed 



