154 ASPARAGIN. 



In plants asparagin, like leucin, is found chiefly in those parts which afford a 

 store of reserve material, such as bulbs, tubers &c. and the cotyledons of seeds. 

 The amount is however largely increased during germination, and it is therefore 

 present in frequently very large quantities in seedlings, as for instance those of 

 yellow lupins (30 p.c.). The increase in the young growing plant is most probably 

 due chiefly to a formation of asparagin out of the decomposition of reserve-proteids, 

 although some may be formed synthetically. The amount is greatest when the 

 seeds are germinated in the dark and the seedling subsequently grown for some time 

 in semi-obscurity and shielded from the access of carbonic anhydride. Under these 

 conditions the formation of non-nitrogenous (? carbohydrate) material is simul- 

 taneously prevented ; and putting the two facts together it appears probable that the 

 disappearance of asparagin in seedlings grown under ordinary conditions is due to 

 its consumption for the synthetic production of proteids 1 . It is conceivable that the 

 amido-acids and amides may similarly play some part in the synthetic metabolism 

 of animal tissues, though to a presumably much slighter extent, bearing in mind how 

 in plants constructive metabolism preponderates so largely over the destructive 2 . 



Asparagin crystallises readily in large rhombic prisms which are 

 not very soluble in cold, but readily soluble in hot water, and are 

 insoluble in absolute alcohol and in ether. Its solutions are dextro- 

 rotatory. It may be prepared synthetically 3 , but is usually obtained 

 by crystallisation from the expressed juice or extracts of the seedlings 

 of peas, beans or lupins 4 . Mercuric nitrate yields a precipitate with 

 asparagin which may be used for its separation from vegetable ex- 

 tracts 5 . Urea-ferment converts it into succinic acid 6 . 



One point of interest with respect to asparagin remains to be 

 briefly mentioned. Seeing that in plants the nitrogen requisite for the 

 construction of proteids appears to be obtained largely from asparagin, 

 is there any evidence that in animals also the nitrogen of this substance 

 can take the place of that of proteids 1 The answer to this question 

 may be stated as follows. When asparagin is administered to carnivora 

 or birds practically the whole of it is converted into urea or uric acid 

 respectively 7 . Thus in carnivora at least there is no diminution of 

 proteid metabolism, such as is observed under a gelatin diet, when 

 asparagin is added to the food. In herbivora on the other hand there 

 appears to be somewhat distinct evidence that a part of the nitrogen in 

 proteids may be replaced by that of asparagin 8 . 



1 Cf. Vines, Physiology of Plants, pp. 124, 150, 174. 



2 Lea, Jl. ofPhysioL Vol. xi. (1890), p. 258. 



3 See recently Piutti, Chem. Centralb. Bd. xix. (1888), S. 1459. 



4 Piria, Ann. de Chim. et de Phys. (3) T. xxn. (1847), p. 160. Schulze u. 

 Bosshard, Zt. f. physiol. Chem. Bd. ix. (1885), S. 420. 



5 Schulze, E., Ber. d. d. chem. Gesell. 1882, S. 2855. 



6 Bufalini, Ann. di chim. e di farmac. (4) T. x. (1889), p. 207. 



7 Von Knieriem, loc. cit. But cf . von Longo, Zt. f. physiol. Chem. Bd. i. (1877), 

 S. 213. 



8 Weiske, Zt. f. Biol. Bd. xx. (1884), S. 277. Weyl, Biol. Centralb. Bd. n. 

 (1882-83), S. 277. These give copious references to literature up to date. In 

 addition see Voit, Sitz. d. Bayr. Akad. 1883, S. 401. Eohmann, Pfliiger's Arch. Bd. 

 xxxix. (1886), S. 21. (On storage of glycogen.) 



