486 ENZYMES 



A like variation obtains in the optimum temperatures of 

 the plant proteolytic enzymes ; for papain it lies between 

 65-70° C, for bromelin it is about 60° C, and for asparaginase 

 it is about 38° C. 



Some doubt has been expressed as to the status of amidases 

 distinct from peptidases. Grover and Chibnall * found that the 

 asparaginase which they isolated from barley roots broke 

 down /-asparagine into aspartic acid, but it had little or no 

 effect on the dextro form of asparagine, a result concordant 

 with that of Ravenna and Bosinelli, f who found that when 

 moulds were grown on a mixture of d- and /-asparagine, the 

 dextro form is unaffected, whilst the laevo form is attacked. 

 The fact that this enzyme also acts on a dipeptide, in the shape 

 of glycylglycine, suggests that asparaginase is in reality a 

 peptidase. And this fact, together with observations on corre- 

 sponding .animal material, suggest that there is no sharp line 

 between peptidase and amidase. 



ZYMASE AND ALCOHOLIC FERMENTATION. 



The formation of alcohol from fluids containing sugar has 

 been known and practised from the earliest times, and the use 

 of yeast in the manufacture of alcoholic beverages and of bread 

 is an ancient industry. As is well known, when yeast is placed 

 in a sugar solution, fermentation begins sooner or later the 

 principal end products being alcohol and carbon dioxide ; 

 substances other than ethyl alcohol, however, are formed, 

 especially glycerol, succinic acid, and amyl alcohol, J the last 



* Grover and Chibnall : loc. cit. 



t Ravenna and Bosinelli : " Atti. R. Accad. Lincei.," 1919. 28, 113. 



X Amyl alcohol, using the term in its general acceptance, is a mixture 



CHaX 

 of two isomeric primary alcohols, isobutyl carbinol ^^^ ^CH . CHj . CHgOH 



CH, 



CH3 



and secondary butyl carbinol CH3 — CHj — CH — CH^OH. The two sub- 

 stances together form " fusel oil," which is the harmful constituent of 

 cheap spirit made from potatoes. 



They appear to be produced from leucine 



(CH3) aCH— CHj— CHNH2COOH, 



CH3 



and isoleucine CH3CH2 — CH — CHNHjCOOH, which are constituents of the 



