THE CHEMICAL PROCESSES IN PLANT RESPIRATION 1 39 



an oxidation of the carbon framework of asparagine, according 

 to Petrow.^ 



If it is conceivable that oxaHc acid may be formed from pro- 

 tein as well as from sugar the possibility of the formation of 

 other organic acids from the cleavage products of the proteins 

 appears to be still greater. Yet the formation of succinic acid 

 from sugar has not been recorded though its formation from 

 glutamic acid is established beyond question.- This process is 

 effected by yeast as follows:^ 



(I) COOH— CHo— CH.2— CH(NH2)— COOH + O - 



COOH— CHo— CH2— CO— COOH + NH3. 



(II) COOH— CH2— CHo— CO— COOH - COOH— 



CHo— CHo— CHO + CO2. 



(III) COOH— CHo— CH2—CHO+ O = COOH — 



CH2— CH2— COOH. 



The circumstance is noteworthy that no nitrogen free acid is 

 furnished when aspartic acid is used by yeast. The process 

 of deaminization of aspartic acid also takes place in seed-plants 

 to an enormous extent when protein is regenerated at the 

 expense of asparagine and soluble carbohydrates. Butke- 

 witsch^ has established beyond doubt that asparagine only 

 serves as a source of N in that ammonia is split off and used to 

 build up the amino acids; but the carbon framework of every 

 amino acid consists of sugar. Hence, one should expect that 

 when protein is regenerated in the growing parts of plants 

 large amounts of the unused residue of asparagine would remain 

 as malic acid or similar compounds. This is not the case, for 

 just as in the deaminization of aspartic acid by yeast, in the 

 utilization of asparagine in germinating plants no nitrogen free 

 residues were found. Kostychev explains this relationship 

 as follows. Malonic acid should come from aspartic acid in 

 the same way that succinic acid is formed from glutamic acid. 



' Petrow, G. G. Stickstoffassimilation durch Samenpflanzen im Lichte und in Dunkel- 

 heit. 1917. Russian. 



2 Ehrlich, F. Biochem. Z. i8: 39i- i909- 



3 Neubauer, O. und Fromherz. Z. f. physiol. Chem. 70: 326. 1911; Neuberg, C. 

 Biochem. Z. 91: 131. 1918. 



< Butkewitsch, W. Biochem. Z. 16: 41 1. 1909141:431. 1912. 



