Enzyme under Varying Concentrations. 259 



In the present paper further experimental evidence for this hypothesis in 

 given, in the case of another hydrolytic enzyme, the vialtase of Aspergillus 

 oryzce (taka-diastase). 



For the extract of Aspergillus oryzce used, the Imperial Cancer Kesearch ' 

 Fund is indebted to Messrs. Parke, Davis and Co., who placed at my 

 disposal one of their most active preparations. This preparation, after being 

 freed from insoluble constituents and purified by a technique to be detailed 

 elsewhere, consists of a white powder, entirely soluble in water, whose 

 activity in maltose is double that of the original preparation. 



The maltose used was Kahlbaum's. It was purified by successive 

 recrystallisations from water, the mother liquor impurities being removed 

 after each recrystallisation by pressing the crystals in an hydraulic press 

 between several layers of clean dry linen. Eventually, after powdering in a 

 mortar and drying for about a week in vacuo over sulphuric acid, a specimen 

 of pure maltose, containing one molecule of water of crystallisation, was 

 obtained. It gave an optical activity = + 130'4°, and its reducing 

 power, determined by Bertrand's method,* was as set out in Table I. 



Table I. 



Weight of maltose. 



Weight of copper. 



mgrm. 



mgrm. 



20 -0 



21 



40 -0 



42-0 



60 -0 



62 -0 



80 -0 



83 -0 



100 -o 



103 -5 



These numbers, allowing for the molecule of water of crystallisation present, 

 correspond exactly with those given by Bertrand (ibid.). 



That the optimum temperature of the ferment is independent of the 

 concentration of the substrate is shown by the following experiments : — Four 

 series of eight clean Jena glass test-tubes were prepared containing respec- 

 tively 360, 180, 90, and 60 mgrm. of maltose dissolved in 4 cm. 3 of water 

 which had been specially purified by redistillation under diminished pressure. 

 Then into each tube was introduced in portions of 1 cm. 3 a solution of the 

 enzyme, prepared a half to one hour previously, containing 10 mgrm. 

 per cm. 3 . The substrate concentrations in the four series of tubes are M/5, 

 M/10, M/20, and M/30. The tubes, after being closed with clean sterile 

 corks, were plunged into water-baths kept at known temperatures. After 



* ' Bull. Soc. Chim.,' (3), vol. 35, p. 1285 (1906). 



