48 ENZYMES AND ENZYM1C ACTIVITIES OF FUNGI 



and other early workers who studied the pathological effects of 

 wood-inhabiting fungi. 



Enzymes of fungi associated with decay of fruits and vege- 

 tables. The literature dealing with the decay of fruits and ve^e- 

 tables abounds in studies on the enzymes produced by the causal 

 fungi. An introduction to the problems involved may be obtained 

 by consulting the publications of Reed (1912), Crabill and Reed 

 (1915), Harter (1921), Harter and Weimer (1921, 1921a), Funke 

 (1922), Muhleman (1925), Davison and Willaman (1927), and 

 Menon (1934). In soft rots of fruits and vegetables, caused by 

 species of Rhizopus, Sclerotinia, Botrytis, and Glomerella, the 

 middle lamellae, or primary host-cell membranes, are attacked by 

 pectinase, and the cells tend to separate intact. These organisms 

 also possess carbohydrases, by means of which they are able to 

 attack starches and sugars in the decay of root and stem crops 

 used by man as food. 



Since soft-rot-producing fungi are of so much economic im- 

 portance, considerable attention has been devoted to their enzymic 

 activities. Studies by Davison and Willaman (1927) involved the 

 pectic enzymes of Botrytis cinerea, Rhizopus tritici, Sclerotinia 

 cinerea, Monilia fructigena, and M. oregonensis. They found, as 

 had other workers, that pectic substances are complex carbohy- 

 drate derivatives composed of three types of materials: ( 1 ) proto- 

 pectin, the parent pectic material which is water-insoluble but 

 which yields pectins on hydrolysis; (2) pectin, the water-soluble, 

 methoxylated, hydrolytic product derived from protopectin; and 

 (3) pectic acid, the water-insoluble, methoxy-free, hydrolytic 

 product. In this hydrolysis three enzymes, protopectinase, pec- 

 tase, and pectinase are involved. Protopectinase attacks the pectic 

 constituents of the middle lamella, pectin is formed, and as a final 

 result the plant tissues are macerated. Pectase is able then to hy- 

 drolyze the pectin to pectic acid, methyl alcohol, and acetone, re- 

 sults which show that pectin is an ester of pectic acid and that 

 therefore pectase is an esterase. Some or all of the products of 

 hydrolysis are utilized as food by the soft-rot-producing species. 



Reed (1912) studied the enzymes, other than pectic enzymes, 

 produced by another soft-rot fungus of apple, Glomerella rufor- 

 maculans and noted that it produced amidase, diastase, emulsin, 

 ereptase, invertase, lipase, protease, and oxidase. 



