IX. METABOLISM 287 



However, if the protein which is to be utilized has the structure 

 entirely dissimilar to the pattern of the assimilase or the protoplasm 

 of the organisms, incorporation following the sole rearrangement may 

 be impossible ; preliminary decomposition appears to be needed in 

 such a case. Presumably reconstruction of a protein from decomposed 

 components may be accomplished with more ease than the rearrange- 

 ment of the pattern without decomposition ; the rearrangement may 

 be impossible because the protein would be disturbed in its structure 

 so profoundly on the adsorption onto the protoplasm that the decom- 

 position would take place before the occurrence of the rearrangement, 

 as the pattern of the protein differs so greatly from that of the pro- 

 toplasm. 



Such a protein in its turn may exert some disturbing influence 

 upon the protoplasm itself because of its foreign structure. This may 

 be the reason why foreign proteins are generally toxic. The rapid 

 decomposition of foreign proteins, therefore, may be needed even for 

 the elimination of their toxic effect. Moreover, decomposed components 

 would be favourable owing to their small molecular state to be 

 transported to another part where the protein synthesis occurs. The 

 function of the reconstruction of specific proteins from foreign ones 

 through the decomposition appears to have already been developed in 

 relative primitive organisms such as protozoa, since in a certain group 

 of protozoa, for example in Paramecium, primitive digestive system 

 can be found. 



A considerable attention seems to be paid on the fact that for the 

 incorporation in vivo and in vitro of any one amino acid into protein, 

 other amino acids are necessary (109). For instance, it has been con- 

 clusively shown that the essential amino acids are not able to sustain 

 growth or even nitrogen balance in an animal when they are fed at 

 intervals, whereas they are effective when fed simultaneously (110). 

 This may be expected if each amino acid is to be adsorbed to the 

 respective pattern of the protoplasm to form a complete peptide chain 

 specific to the organisms. 



It has frequently been suggested' that the most primeval organisms 

 might utilize the sunlight energy by chlorophyll. The writer claims, 

 however, that organisms never acquired the faculty to yield chloro- 

 phyll until they evolved up to a considerably high stage. It is en- 

 tirely inconceivable that primeval organism could synthesize an- 

 enzyme so highly developed as chlorophyll. Nevertheless, it may be 

 possible that primeval organisms could synthesize proteins from car- 

 bon dioxide and ammonia or other N-compounds by making use of the 

 sun energy, even long before they could yield chlorophyll, but because 

 of the non-development of the perfect synthesizing system, the syn- 



