CASUAL UKINARY CONSTITUENTS. 775 



R.COOH. The appearance of lactic acid in the urine of rabbits after 

 feeding alanine is an example of such deamidation. 1 The possibility 

 is not excluded that in the first place the keto-acid, pyruvic acid, 

 CH 3 .CO.COOH, is formed from the alanine and then the lactic acid, 

 CHs.CHOH.COOH, formed from this as a secondary reduction product. 



In agreement with the views of NEUBAUER 2 it is now rather 

 generally conceded that the hydrolytic deamidation is not as important 

 as the oxidative deamidation, with the formation of keto-acids 

 R.CH(NH 2 ).COOH+O = R.CO.COOH+NH 3 , although this is not the 

 only possibility. The proofs for the correctness of this view have been 

 obtained essentially by experiments with aromatic amino-acids and 

 will be given as examples of such deamidation. 



DAKIN and DUNDLEY 3 have shown that all a-amino-acids investi- 

 gated by them can be decomposed under special conditions so that they 

 to a certain degree yield ammonia and an a-keto-aldehyde. 



R.CH.NH 2 .COOH^R.CO.CHO+NH 3 . 



Thus, with alanine, and as the reaction to all appearances is reversible, 

 they consider the relationship between alanine and lactic acid is as follows : 



CHs.CH.NHa.COOH^CHa.CO.CHO^CHsCHOH.COOH. 



They also found it probable, that the a-keto-aldehydes represent the 

 first step in the demolition of the a-amino-acids whereby the regular 

 demolition of these acids takes place over the a-keto-acids and not over 

 oxyacids, which explains also the formation of sugar from certain amino- 

 acids (over methylglyoxal as intermediary step). 



The deamidation after previous oxidation with the formation of 

 keto-acids has awakened special interest because recently in perfusion 

 experiments on dog-livers the reverse process, namely a synthesis of amino- 

 acids from keto-acids (in part also from oxyacids) and ammonia has been 

 performed (KNOOP, EMBDEN and SCHMITZ, KoNDO 4 ). Among such 

 syntheses we can here call attention to the synthesis in the dog-liver 

 of alanine, phenylalanine and tyrosine from pyruvic acid (also lactic acid), 

 phenylpyruvic acid and p-oxyphenyl pyruvic acid, or of a-amino-n-butyric 

 acid from a-keto-butyric acid (all as ammonium salts). 



1 See Langstein and Neuberg, Arch. f. (Anat. u.) Physiol., 1903. Suppl. Bd. 

 Deutsch. Arch. f. klin. Med., 95, and Habilit. Schrift., Leipzig, 1908. See also 

 further on in regard to the literature on the demolition of the aromatic amino-acids. 



3 Journ. of biol. Chem., 14. * 



4 Knoop, Zeitschr. f. physiol. Chem., 67 and 71; Embden and Schmitz, Bioch. 

 Zeitschr., 29 and 38; Kondo, ibid., 38. 



