u8 THE PHYSIOLOGY OF PROTEIN METABOLISM 



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in the presence of carbohydrates and fats, and they also reached the 

 conclusion that carbohydrate was absolutely essential to the animal 

 organism. They state definitely that retention of nitrogen only takes 

 place in the presence of carbohydrates. Shaffer and Coleman (370) 

 have demonstrated clearly that the " toxic " destruction of body pro- 

 tein in fever may be largely prevented by the intake of carbohydrate. 

 The observations of the botanical physiologists also support such a 

 contention. Hansteen (169), Ivanoff and others have repeatedly de- 

 monstrated that the presence of carbohydrate is absolutely essential 

 before protein synthesis can take place in plants. Ivanoff (209) found 

 that the synthesis of the organic phosphorus compounds in yeast did 

 not take place in the absence of the decomposition products of sugar 

 which are formed during alcoholic fermentation. The phosphoric 

 'acid is supposed by him to combine with an aldehyde-ketone group. 

 Czapek (104) found that moulds did not grow well in a medium con- 

 taining an abundant supply of amino acids, or other suitable nitrogen 

 compound, if carbohydrate were absent He found that the carbo- 

 hydrate, which was most readily utilized, was glucose. Kinoshita (220) 

 and Suzuki (390) carried out a series of experiments in plants and 

 concluded that ammonia could be taken up from without and be con- 

 verted into asparagine, if a sufficiency of carbohydrates were present. 



Intracellular Synthesis, (a) In vitro Experiments. 



Until recently no experimental work on the possible nature of this 

 intracellular synthesis existed. Pfliiger had suggested that the part of 

 the decomposed protein molecule which was nitrogen-rich combined 

 with " alcohol radicles " to form new protein. There is much in vitro 

 work which offers valuable suggestions as to the probable nature of the 

 processes which occur. It has long been well known that aldehydes 

 form compounds with many different substances containing nitrogen, 

 e.g. aldehyde ammonia. Sugars have also been shown to react like 

 the simple acetaldehyde ; Lobry de Bruyn (257) made compounds of 

 sugar with ammonia. Other nitrogenous substances, more complex 

 than ammonia, have also been shown to unite with different aldehydes : 

 Morrell and Bellars (290) have obtained a definite compound of glu- 

 cose and guanidine, and Wolfe (423) has prepared the compound with 

 aminoguanidine. Schoorl (358) has made a compound of glucose and 

 urea, and Jaffe (2 1 2) a compound of creatine or creatinine and formalde- 



