MALTASE. 523 



contain a larger or smaller quantity of maltose, according as the 

 beer is to be lightly fermented and full flavoured, or highly 

 fermented and vinous. In this connection it is customary to 

 speak of the " attenuation " (degree of fer mentation) of the beer, 

 which, however, does not depend solely on the mashing process, 

 but also on the kind of pitching yeast (see p. 268, vol. ii.) 

 employed. 



Though maltose can be hydrolysed by acids, the transforma- 

 tion which results in the production of two molecules of d-glucose 

 is far less easily effected than is the case with saccharose. On 

 the other hand, maltose is readily decomposed by the yeast enzyme 

 maltase. A similar enzyme was discovered in maize by GEDULD 

 (II.), who termed it "glucase"; but later workers, including 

 LINTNER and KROBER (I.) have shown them to be different. 



Maltase was discovered in yeast by EMIL FISCHER (VII.), after 

 LINTNER (X.) had indicated the possibility of yeast possessing 

 an enzyme capable of decomposing maltose. The original name 

 for the enzyme was glucase or glycase, it being also called yeast 

 glucase for closer identification ; but at that time the nomenclature 

 of the enzymes was in a state of confusion, some of them being 

 named after the products to which they give rise, and others after 

 the sugars they decompose (compare W. WINDISCH (V.) ) and it 

 was only later that the term maltase found general acceptance 

 for the enzyme that decomposes maltose. In order to obviate 

 any uncertainty, E. 0. von LIPPMANN (IV.) proposed a new ter- 

 minology, according to which the enzymes were to receive double 

 names, the first portion indicating the sugar decomposed, and the 

 second the product, or main product of the hydrolysis. Under 

 this proposal the enzyme decomposing maltose would be termed 

 maltoglycase or maltoglucase ; but this name has not come into 

 favour. 



Maltase occurs in all races of culture yeasts of the Sacch. 

 cerevisice group belonging to the UF, US, OF, and OS types, as 

 well as all wine yeasts (compare pp. 278-280, vol. ii., and p. 283 

 et seq. vol. ii.). Special interest attaches to HARTMANN'S (I.) Torula 

 colliculosa (see p. 397, vol. ii. ). As already mentioned, maltase also 

 occurs in maize; likewise in mould fungi (see p. 362, vol. ii.), 

 turnips, peas and potatoes, as well as in cereals (compare 

 BEIJERINCK (XIII.), and STOKLASA and CZERNT (I.)). The low 

 enzymatic influence exerted on maltose by barley leads to the 

 supposition that, as in the case of wheat, rye, and rice, maltase is 

 not inherent in this cereal, its presence being due to adherent mould 

 fungi and yeasts (see p. 533, vol. ii.). Researches on this point 

 would add to our knowledge on the occurrence of the maltases. 



The preparation of " pure " maltase is attended with difficul- 

 ties. On the one hand, according to E. FISCHER (VII.), and 

 LINTNER and KROBER (I.), this enzyme is only sparingly soluble 

 in water, and, on the other, it is very susceptible to alcohol, which 



