108 CARBON METABOLISM II 



enzymatic entity. Transglucosidases which act on maltose to form 

 polysaccharides are known in bacteria but have not yet been reported 

 from fungi. 



The disaccharide lactose is split to its constituent hexoses by the 

 enzyme lactase, a /?-galactosidase. The enzyme has been reported in 

 several fungi and actinomycetes, but is apparently not of such general 

 occurrence as either sucrase or maltase. Some of the early work on 

 lactase in commercial enzyme preparations and in basidiomycete 

 sporophores may be open to question because of the possibility of 

 bacterial contamination. 



The adaptive formation of lactase in Neurospora crassa has been 

 proved (Chapter 3). A purified enzyme from Aspergillus oryzae acts 

 as a transgalactosidase; galactose residues are transferred to alcohols, 

 to lactose itself to form a trisaccharide, or to water to yield free 

 galactose (Table 1). Whether all action of lactase can be credited to 

 this enzyme is not yet known. 



Cellobiose is formed during the hydrolysis of cellulose. Although 

 it is common to refer to the enzyme splitting it as cellobiase, there is 

 no reason to think that this enzyme differs in any way from /3-glucosi- 

 dases acting on other /3-glucosides. Specific assays with cellobiose as 

 substrate have been made infrequently, but it seems that most fungi 

 can split it to its constituent glucose residues (191). Resting and 

 growing cells of Aspergillus niger form new oligosaccharides from 

 cellobiose (11, 12), and additional evidence for transglycosidase action 

 on cellobiose has been obtained with other fungi (Table 1). Cellobiose 

 is synthesized by Ustilago zeae as a component of ustilagic acid (128). 



Trehalose, an a-glucosido-glucose, is not attacked by the usual 

 a-glucosidases but rather by a special enzyme, trehalase, found in 

 animals, plants and fungi (89). Early work on trehalase in fungi is 

 reviewed by Czapek (59); this and more recent data indicate the 

 enzyme is common (203, 256). The spores of Aspergillus luchuensis 

 contain measurable amounts of the enzyme (139). In Lycogala sp., 

 a myxomycete, trehalase of the fruit body disappears during ripening 

 (108). 



Trehalose is the only disaccharide to be formed free in appreciable 

 amounts by fungi. The discovery of the sugar in ergot (Claviceps 

 purpurea) by Wiggers (254) and early reports of its occurrence in other 

 fungi are reviewed by Zellner (264) and Obaton (164). Trehalose is 

 especially common in the basidiomycetes but is found also in many 

 other fungi (34, 36). Usually it constitutes 2 to 3 per cent of the 

 mycelial dry matter (108, 193, 227). 



In all probability, trehalose in fungi has the role of a translocatable 



