THE CHEMICAL CONSTITUTION OF ITS UNITS 59 



NH 2 NH 2 



NH = C NH CH 2 CH 2 CH 2 CH COOH + O 2 = CO 2 + NH 3 + 

 NH 2 



NH = C NH CH 2 CH 2 CH 2 COOH 



NH 2 NH 2 



NH=:C NH CH 2 CH 2 CH 2 -COOH + O 2 = NH = C NH 2 + 

 HOOC CH 2 CH 2 COOH 



Lysine. 



Lysine was discovered by E. Drechsel amongst the decomposition 

 products of caseinogen in 1889, and its presence in other proteins 

 gelatin, egg-albumin, conglutin, fibrin was shown by his pupils, Ernst 

 Fischer, Siegfried and Hedin. It was found by Kutscher in antipeptone 

 and by Kossel in the protamines. Its occurrence in germinating seed- 

 lings was demonstrated by Schulze and in vegetable proteins by Schulze 

 and Winterstein. Thus, like arginine and histidine it is a very widely 

 occurring constituent of the proteins. 



Drechsel gave it the formula C 6 H 14 N 2 O 2 and regarded it as a 

 diaminocaproic acid ; Ellinger proved in 1 899 that it possessed this 

 constitution, by obtaining cadaverine from it by putrefaction, which 

 showed that the two amino groups were in the a, e-positions : 



NH 2 .CH 2 .CH 2 .CH 2 .CH 2 .CH(NH 2 )COOH = 

 CO 2 + NH 2 . CH 3 . CH 2 . CH 2 . CH 2 . CH 2 . CH 2 . NH U . 



Henderson's experiments also showed that lysine must have this consti- 

 tution, namely, a, e-diaminocaproic acid. Its constitution was only 

 definitely determined by synthesis by Fischer and Weigert by the 

 following method : 



When 7-cyanopropylmalonic ester is treated with nitrous acid, it 

 loses one of its carboxethyl groups and is converted into a-oximido- 

 S-cyanovalerianic acid, which on reduction with sodium amalgam yields 

 a, e-diaminocaproic acid, thus : 



xCOOC 2 H 5 

 NC . CH 2 . CH 2 . CH 2 . CH^f _> NC.CH 2 . CH 2 . CH 2 . C( = NOH) . COOC 2 H 5 -> 



X COOC 2 H 5 

 H 2 N . CH 2 . CH 2 . CH 2 . CH 2 . CHfNHa) . COOH 



