202 THE CARBOHYDRATES 



The optimum hydrogen ion concentration of the pectase 

 from currants was found by Euler and Svanberg * to be 



Ph4-3- 



While Bertrand and Mallevre showed that the presence 



of calcium salts was essential for the production of a gel, 



Goyaudf came to the conclusion that the activity of the 



enzyme was in no way dependent upon the presence of 



calcium salts inasmuch as it was able to break down the 



pectin to pectic acid even in solutions which had been deprived 



of calcium salts by the addition of potassium oxalate ; the 



addition of calcium salts to such solutions, however, at once 



produced a gel owing to the precipitation of the insoluble 



calcium pectate. It is concluded from this that the function 



of calcium in this connection is only to reveal the products 



of the activity of the hydrolytic enzyme ; if this be the true 



explanation, it is a very remarkable fact that pectase should 



in many cases be able to effect hydrolysis of pectin in less 



than one minute, although it must be borne in mind that the 



hydrolysis by means of caustic soda likewise is completed in 



a very short time (cf. p. 198). 



Another enzyme, pectinase, was first described by 

 Bourquelot and Herissey % as occurring in malt and was later 

 found by Ehrlich in takadiastase ; this enzyme also acts 

 hydrolytically upon pectins but breaks them down further 

 than pectase, past the pectic acid stage to the yielding of 

 reducing sugars. This enzyme is said to be the one secreted 

 by Granulohacter pectinovorum, and Bacillus carotovorus. An 

 enzyme having similar properties has been described by 

 Kylin § as occurring in marine algae. 



Pectins are also subject to attack by enzymes secreted by 

 various fungi and other bacteria, though the exact nature of 

 the products of their activity has yet to be studied. Thus 

 it was shown by de Bary that Peziza sclerotiorum destroys the 

 host plant by disintegrating the cell walls owing, presumably, 



* Euler and Svanberg : " Biochem. Zeit.," igig, 100, 271. 

 jGDyaud: "Compt. rend.," 1902, 135, 537. 



t Bourquelot and Herissey : " J. Pharm. et Chim.," 1898, [6], 8, 145 ; 

 1899. [6], 9, 563, and 10, 5. Also Verdon : " J. Pharm. Chera.," 1912, 



5. 347- 



§ Kylin : " Zeit. physiol. Chem.," 1915, 94, 412. 



