Sect. V, 1922 [75] Trans. R.S.C. 



XIII. A Preliminary Study of the Action of Arginase and of its Possible 

 Use in the Determination of A rgini?ie 



By Andrew Hunter, M.A., F.R.S.C., and J. A. Morrell, B.A. 



(Read May Meeting, 1922) 



It has been proposed by B. C. P. Jansen^ that the quantity of 

 arginine in a protein hydrolysate should be estimated by subjecting 

 it to the combined action of the two enzymes arginase and urease, 

 and determining the amount of ammonia (as carbonate) thus pro- 

 duced. Such a method, if its accuracy could be relied upon, would 

 have numerous useful applications; and we have therefore undertaken 

 to study its possibilities. 



Before this could be done in any systematic way it was necessary 

 to have on hand some optically pure c?-arginine. A quantity of 

 the base, prepared from gelatin, was accordingly very carefully 

 purified, converted into the hydrochloride, and as such crystallized 

 twice from 70% alcohol. This product, polarised in approximately 

 11% concentration and in the presence of 7 moles of fre^ HCl, gave 



H 20° 

 P^ = +21.95°, from which may be calculated for the free base a 



specific rota'ory power of +26.54° These figures ae higher than 

 Gulewitsch's,2 who found +21.22° and +25.66° respectively. We 

 conclude that the rotatory power of fZ-arginine is higher than has 

 been hitherto supposed, and that our preparation was in all probability 

 free from contamination with racemic arginine. 



In one of several preliminary experiments 36.77 mgm. of the 

 above hydrochloride, dissolved in 2 c.c. of water was treated with 

 3 c.c of a neutra' phosphate mixture, 2 c c. of a neutralized arginase 

 solution, and a few drops of toluene; after the mixture had stood 

 overnight at room temperature the urea produced was determined 

 by the urease method according to the technique of Van Slyke and 

 Cullen. The amount of urea nitrogen found was 4.80 mgm., which 

 is 98.2% of the theoretically possible 4.89. It appears therefore 

 certain that the decomposition of arginine by arginase may, under 

 certain conditions, be practically, if not absolutely, quantitative. 

 In other experiments the yield was much less satisfactory, often as low 

 as 72%. Evidently the conditions leading to a satisfactory result 



IB. C. P. Jansen: Chem. Weekblad, xiv, p. 125 (1917). 



W. Gulewitsch: Zeitschr. f. physiol. Chem., xxvii, p. 178 (1899). 



