INVERTASE. 521 



DUCLAUX (XXIX.), O'SULLIVAN and TOMPSON (I.), and FERNBACH 

 (VI.) to have strongly adverse influence, even in small quan- 

 tities. According to NASSE (II.) and DUCLAUX (XXIX.), small 

 quantities of alkali chlorides and calcium chloride have a beneficial 

 effect, whilst salts of the heavy metals are injurious. Alcohol, 

 even as little as 5-10 per cent., is stated by A. MAYER (XV.), 

 J. MORITZ (III.), and O'SULLIVAN and TOMPSON (I.) to have a 

 restrictive influence on hydrolysis; and, according to GRIFFITH 

 (I.), small quantities of salicylic acid have a similar effect. 



In contrast to other enzymes, invertase seems to be completely 

 inalterable. A. MAYER (XVI.) found that it is not attacked by 

 putrefactive bacteria, although his experiment was not entirely 

 free from objection, it being stated by FERMI and MONTESANO (I.) 

 that certain bacteria themselves produce invertase, so that there 

 is no proof whether the invertase found in the products of putre- 

 faction really originated in the yeast or were excreted by the 

 bacteria. BAU (XXVI.) investigated the mutual interaction of 

 yeast enzymes, of which yeast-endotryptase (see chap. Ixvi.), or 

 yeast-peptase alone come under consideration. Yeast that had 

 been liquefied at 45 0., or expressed yeast juice that had been 

 kept for one to three weeks at i7-2o C., or heated at 30 C. or 

 40 0. for an hour, still contained unimpaired invertase. The 

 activity of this enzyme also remained intact when the yeast was 

 digested for twenty- four hours at 37 C. with a solution containing 

 the extremely large quantity of i per cent, of pepsin (Merck) 

 and o.i per cent, of hydrochloric acid. It is true that, in these 

 experiments, nothing was done to ascertain the quantities of 

 invertase before and after the treatment with yeast endotryptase 

 and pepsin respectively. 



Attempts have already been made at the quantitative deter- 

 mination of invertase; but the method proposed by FERNBACH 

 (VIII.), like all quantitative methods for the determination of 

 enzymes, is attended by the drawback that only the effect of the 

 enzyme can be measured and not the amount of enzyme actually 

 present. According to Fernbach, a number of samples (each 

 measuring exactly 4 c.c.) of a 50 per cent solution of saccharose 

 are treated with i, 2, 3, &c., c.c. of the invertase solution under 

 examination, each of the mixtures being then treated with i c.c. 

 of decinormal acetic acid and made up to 10 c.c. The test- 

 glasses are then warmed to 56 C. for an hour on the water-bath, 

 cooled quickly and treated with a few drops of caustic soda to 

 destroy the enzymatic action, the amount of invert sugar formed 

 being determined by means of Fehling's solution. Fernbach 

 estimates the unit of invertase as that capable of hydrolysing 0.2 

 grin, of saccharose in one hour at 56 C. and in presence of i per 

 cent, of acetic acid. 



According to MORITZ and MORRIS (I.), the hydrolysis of 

 saccharose by invertase is utilised in certain English breweries 



