532 ENZYMES DECOMPOSING SACCHARIDER. 



animals. It occurs in the mucous membrane of the stomach and 

 intestines of infants and young animals, according to the state- 

 ments of PAUTZ and YOGEL (IV.), WEINLAND (I.), FISCHER and 

 NIEBEL (I.), and other workers. 



The expressed juices recovered by STOKLASA and CZERNY (II.) 

 from muscle, liver, lungs, and other organs, decompose and ferment 

 milk sugar ; and according to SIMACEK (II.), lactase is also present 

 in pancreatic juice. 



According to Weinland, the optimum temperature for lactase 

 is 39 C. ; but comprehensive research is needed on this point, as 

 well as on the destruction temperature, and the favourable or 

 adverse influence of chemicals and other substances on the enzyme, 

 these properties of lactase being still undetermined. 



Like maltase (see p. 525, vol. ii.), the remarkable property of 

 reversion is also exhibited by lactase, especially that from kefyr. 

 If 200 c.c. of extract kefyr granules be treated with 100 grms. of 

 fZ-glucose and 100 grms. of r^-galactose, in presence of 10 c.c. of 

 toluene, and the mixture be kept in a tightly closed flask for fif- 

 teen days at 35 C., it is stated by E. FISCHER and ARMSTRONG (I.), 

 that the mixture will furnish a new disaccharide, which they term 

 isolactose. This sugar is split up a.gain into c^-glucose and cZ-galac- 

 tose by a dilute solution of kefyr lactase, though not by emulsin . 

 A highly interesting observation by E. Fischer and Armstrong 

 is that isolactose is fermented by bottom yeast, but not by top yeast, 

 the sugar thus behaving like melibiose with regard to these two 

 races of yeast. 



331. Trehalase. 



The sugar, trehalose, consists of two molecules of cZ-glucose. 

 which, however, are combined in a different manner from the two 

 groups of grape sugar composing maltose, isomaltose, turanose, 

 and probably other disaccharides, such as HILL'S (I.) revertose. 

 They are hydrolysed with great difficulty by acids, the decomposi- 

 tion of over 99 per cent, of trehalose necessitating boiling for six 

 hours with 5 per cent, sulphuric acid. 



This sugar was formerly regarded as unfermentable, until 

 Boning showed that the same " begins to ferment at the end of 

 twelve hours in presence of best quality yeast that has been 

 sufficiently washed " ; compare TOLLENS (VII.). 



BOURQUELOT (XIII.) afterwards discovered in Aspergillus niger 

 (see p. 363, vol. ii.), an enzyme decomposing trehalose. For the 

 preparation of this, trehalase or trehalo-glucase, according to the 

 nomenclature proposed by E. O. VON LIPPMANN (IV.) he culti- 

 vated the mould fungus on Raulin's nutrient solution, triturated 

 the culture with sand, extracted the water by means of 95 per 

 cent, alcohol, and dried the residue in vacua, the mass being 

 then extracted with water and the filtrate precipitated with 

 alcohol. The resulting mould-fungus trehalase, which also occurs 



