Abstract
A delicate method of estimating invert activity (sucrase) would be of advantage in connection with a number of physiological problems. A substitution of one per cent. cane sugar for the one per cent. soluble starch or glycogen, employed by Myers and Killian, 1 in the estimation of the diastatic activity of the blood, furnishes a very delicate method for sucrase.
The technic of the method is as follows: To 8 c.c. of water in a 50 c.c. centrifuge tube is added 1 c.c. of the extract to be examined, and the solution warmed to just 40° C. in a water bath with thermostat attachment. One c.c. of one per cent. cane sugar is now added and incubation carried out for 30 minutes. The solution is rapidly cooled in cold water and 0.5 to 1.0 gram of dry picric acid added, thoroughly mixed, centrifuged and filtered. The inverted sugar is now estimated colorimetrically in 3 c.c. portions as already described. 1
One must not let the sucrose stand for a long time in contact with the picric acid, owing to the hydrolytic action of the picric acid. 2 For this reason it might be of advantage to employ sodium picrate, as recently recommended by Benediet. 3
Utilizing the above method we have been unable to satisfactorily demonstrate sucrase in human blood or that of rabbits. With one per cent. yeast extract there was 60 per cent. inversion in one-half hour, i. e., 6 of the 10 mg. were inverted, while a one per cent. yeast extract in human blood gave a 54 per cent. inversion. With a 10 per cent. extract of the mucous membrane of rabbit's intestine figures of 13.2 and 12.8 per cent, were obtained. Controls were all negative.
Get full access to this article
View all access options for this article.