1244 



LEUCINE. 



6. Diamido-valerianic acid. [C 4 H 7 (NH 2 ) 2 . COOH]. 



When benzoic acid is administered to fowls it is not con- 

 verted into hippuric acid as it is in mammals (see p. 1278), but 

 gives rise to an acid called ornithuric. When this is boiled 

 with hydrochloric acid it splits up into benzoic acid and a 

 base called ornithin, which has the composition of diamido- 

 valerianic acid. 



7. Leucine. C 6 H 13 N0 2 (a-Amido-caproic acid). Recent 

 research has shewn that of the various possible isomeric amido- 

 caproic acids the leucine dealt with by physiologists is a-amido- 

 isobutylacetic acid, (CH 3 ) 2 CH . CH 2 . CH (NH 2 ) . COOH. 



It is a characteristic product of the decomposition of pro- 

 teids and gelatin whether by the action of boiling acids, caustic 

 alkalis or putrefactive influences. It occurs normally in variable 

 amounts in the pancreas, spleen, thymus, thyroid, salivary glands, 

 liver, etc., and also in plants, more especially in those parts in 

 which reserve materials are accumulated, such as bulbs, tubers 

 and seeds. It is also typically formed during the tryptic (pan- 

 creatic) digestion of proteids to an extent which amounts on 



Fig. 202. Leucine Crystals. (Krukenberg.) 



the average to some 8 — 10 p.c. on the proteid digested, and is 

 in this case always accompanied by tyrosine. It may occur in 

 the urine, more particularly in cases of acute yellow atrophy of 

 the liver ; but its presence in this excretion in other and more 

 general diseased conditions of the liver is by no means so con- 

 stant or certain as it presumably would be on the common 

 assumption that a large part of the urea leaving the body is 

 due to its formation from leucine under the converting action 

 of the liver. 



As usually obtained in a more or less impure form it crys- 

 tallizes in rounded fatty -looking lumps which are often collected 



