420 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Zymase. 



The activity of zymase is measured by estimating the amount of carbon 

 dioxide which is evolved. This is effected most simply by determining the 

 loss in weight : 20 c.c. or a known volume of zymase solution are placed in 

 an Erlenmeyer flask with a known amount of sugar solution and i per cent. 

 of toluene is added. The flask is closed with a Meissl tube and the loss in 

 weight determined. 



It may also be determined by mixing known amounts of the zymase 

 solution with sugar solution and some toluene in a flask connected to 

 another flask containing excess of N sodium hydroxide. The first flask is 

 fitted with a valve and the second, containing the sodium hydroxide, is con- 

 nected with a soda lime tube. Air is sucked through the flask at the end 

 of the experiment through the sodium hydroxide, the enzyme solution being 

 boiled to expel the last trace of carbon dioxide. The sodium hydroxide 

 solution is titrated firstly against phenolphthalein and secondly against 

 methyl orange. The difference in the values gives the amount of carbon 

 dioxide. 



Harden, Thompson and Young * have described a very accurate method 

 in which the estimation is effected volumetrically. 



Lipase. 



Lipase acts upon fats producing fatty acids. Its activity is measured 

 by titrating the mixture of enzyme, fat and fatty acids. A known volume 

 of enzyme solution is added to a known amount of ester (ethyl butyrate), 

 of fat (neutral olive oil), or egg-yolk, suspended in water ; the mixture is kept 

 at 37 and titrated after 2-24 hours. A control is made with boiled enzyme 

 or a similar mixture titrated immediately after the addition of the enzyme 

 solution. 



1 Biochem. J., 1910, 5, 230 ; see also Harden's monograph on " Alcoholic Fermentation ". 



