14 BULLETIN 158, U. S. DEPARTMENT OF AGRICULTURE. 



were able to convert ade nine and guanine into hypoxanthine and 

 xanthine. They also show that the bacteria have the power of split- 

 ting the nucleic acid itself. This same change is also brought about 

 by the action of certain enzymes, such as erepsin, on nucleic acid. 



With these facts at hand it is possible to draw the following con- 

 clusions as to the source of the two purine bases in this fertilizer: 

 The guanine and hypoxanthine may be derived from plant remains 

 which originally contained these two compounds; the guanine may 

 arise by the acid hydrolysis of certain vegetable or animal nucleo- 

 proteins which were present in the original materials; and the 

 hypoxanthine may have been formed by the processes of natural 

 decomposition, such as the action of bacteria ^nd enzymes, which had 

 taken place in the crude materials before they were subjected to the 

 acidulation process or during the process itself. It is not improbable 

 that the guanine and hypoxanthine come from all of these sources. 



Diamino acids. — Of the three diamino acids lysine was obtained in 

 much the largest amount, arginine next, and histidine in the smallest 

 amount. These compounds are products of protein hydrolysis by 

 acids, but may also be produced under certain conditions by the 

 action of bacteria. Since one or more of the diamino acids have 

 been found to be present in every protein so far examined, and since 

 the method for the analysis and the isolation of these bases is almost 

 quantitative, the determination of the number and amounts of the 

 diamino acids present in a mixture of protein hydrolysis products is 

 of importance in deciding the nature and character of the original 

 material which entered into the processed goods. 



Monoamino acids. — Although leucine and tyrosine, which are pro- 

 tein decomposition products, were found in about 'the same quanti- 

 ties, the methods of isolation were so far from being quantitative 

 that this relationship is of no significance. The isolation and identi- 

 fication of the other monoamino acids from the complex products of 

 protein hydrolysis can only be accomplished, in the majority of 

 cases, by means of the esterification method of Emil Fischer. This 

 method is not a strictly quantitative one and requires large amounts 

 of materials for a successful separation, and consequently was not 

 used in this investigation. The use of methods other than that of 

 esterification failed to isolate any other monoamino acid in quantities 

 large enough for identification. As will be shown later, a number of 

 monoamino acids besides the two isolated must be present in the 

 processed goods. 



Establishing the presence of these products of acid hydrolysis of 

 proteins, namely, the diamino acids, arginine, lysine, and histidine, 

 and the two monoamino acids, leucine and tyrosine, in the amounts 

 in which they were found is of itself sufficient evidence to demonstrate 

 that by the acid treatment of the crude materials used in the manu- 



