ENZYMES 49 



endolipases are known. Many fungi store fat as reserve material, and 

 presumably the first step in utilization is hydrolysis. 



Phosphatases are classified as esterases because of the fact that they 

 catalyze the hydrolysis of esters of phosphoric acid. Phosphorus is an 

 essential element which enters into many metabolic processes and is a 

 constituent of many physiologically important compounds. Many 

 coenzymes are esters of pyrophosphoric acid (thiamine pyrophosphate, 

 and diphosphopyridine nucleotide, DPN), while triphosphoric acid is a 

 constituent of triphosphopyridine nucleotide, TPN. The synthetic 

 capacity of the phosphatases has been rarely demonstrated. Other 

 enzymes, phosphorylases, are apparently the catalytic agents active in 

 forming many phosphate esters. In many instances the substrates from 

 which these esters are formed are different from the products of phos- 

 phatase hydrolysis. 



Carbohydrases. The enzymes which catalyze the hydrolysis of com- 

 plex carbohydrates, or polysaccharides, are called carbohydrases. These 

 enzymes appear to be highly specific ; thus each of the common disaccha- 

 rides requires a different enzyme for hydrolysis. Sucrase is found in 

 many fungi, including the common strains of Saccharomyces cerevisiae, 

 although it is apparently absent in Schizosaccharomyces octosporus. The 

 enzyme which hydrolyzes maltose to glucose is called maltase. Maltase 

 is very widely distributed among the fungi. The enzyme which catalyzes 

 the hydrolysis of lactose to glucose and galactose is called lactase. While 

 this enzyme is less widely distributed among the fungi than sucrase and 

 maltase, it is produced by many species. 



While it is doubtless correct to assume that the more complex and in- 

 soluble carbohydrates must be hiydrolyzed before utilization, this assump- 

 tion may, in some instances, be false with regard to the disaccharides. It 

 is possible that some fungi may employ a phosphorylative degradation of 

 the disaccharides rather than hydrolysis. For a critical review of carbo- 

 hydrate utilization without preliminary hydrolysis, see Hestrin (1948). 



In addition to the water-soluble polysaccharides there is a wide variety 

 of water-insoluble high-molecular-weight carbohydrates which are utilized 

 by many fungi as carbon sources. Only two of these complex polysaccha- 

 rides will be considered here. The empirical formula for cellulose is 

 (C6Hio05)„. On complete hydrolysis by acids, glucose is the only prod- 

 uct. Less complete hydrolysis produces a disaccharide known as cello- 

 biose. The majority of fungi, according to Norman and Fuller (1942), 

 are able to attack cellulose. The early work is reviewed by Thaysen and 

 Bunker (1927). With respect to the fungi which attack cellulose, a great 

 deal of variation in cellulolytic ability is found (see White et al., 1948). 

 The enzyme which catalyzes the hydrolysis of cellulose is called cellulase. 



While starch has the same empirical formula as cellulose, it is more 



