On the Origin of the Fore-protein 



SHIRO AKABORI 



Institute for Protein Research, Osaka University, Osaka 



If protein is absolutely essential for all living things, the very beginning of life 

 must have been a spontaneous formation of protein at a certain age of the Earth. 



In 1936 Oparin [i] postulated that a-amino acids could have been formed 

 non-biologically from hydrocarbons, ammonia and hydrogen cyanide at the age 

 of the Earth when the atmosphere contained these substances in high concen- 

 trations. Bernal [2] emphasized the role played by ultraviolet hght in the 

 formation of organic compounds at a certain stage of the evolution of the Earth. 

 He also suggested that life might have originated on the surface of clay which 

 accumulated large amounts of organic substances. Oparin's hypothesis has 

 received strong experimental support from the recent work of Miller [3]. 



It has generally been beUeved that the first proteins or fore-proteins were 

 non-biologically formed by the polycondensation of preformed free amino acids. 

 This behef is solely based on the fact that proteins in present-day organisms are 

 synthesized via free amino acids. Such non-biological formation of polypeptides 

 and proteins, however, seems to be very difficult owing to the requirement of 

 free energy, though Bresler [4] reported the reconversion of tryptic hydrolysates 

 to the original proteins under an extremely high pressure. 



In 1955 I proposed [5] a hypothesis concerning the origin of the fore-protein 

 and speculated that it must have been produced through reactions consisting 

 of the following three steps. 



The first step is the formation of aminoacetonitrile from formaldehyde, 

 ammonia and hydrogen cyanide. 



CH2O + NH3 + HCN > H2N— CH2— CN 



The second is the polymerization of aminoacetonitrile on a solid surface, 

 probably in the state adsorbed on clay, followed by the hydrolysis of the polymer 

 to polyglycine and ammonia. 



+ XH2O 



X H2N— CH2— CN > (— NH— CH2— C— )x > (— NH— CH2— CO— )x + x NH3 



II 

 NH 



and the third step is the introduction of side chains into polyglycine by the 

 reaction with aldehydes or with unsaturated hydrocarbons. 



I have also pointed out that the formation of amino acid residues possessing 

 the same configuration throughout one single peptide chain could be expected 

 from this mechanism, assuming that the configuration adsorbed on the soHd 

 surface is the aV-form, as shown in Fig. i. 



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