ACTION OF THE ENZYMES. 103 



reaction which occurs also in its absence, only then exceed- 

 ingly slowly. Starch paste by itself kept at a suitable tem- 

 perature is very slowly converted into maltose. Amylase 

 is therefore a positive catalyzer. The influence of tem- 

 perature upon the activity of this ferment has been 

 worked out by KJELDAHL. At C. amylase acts exceedingly 

 slowly, but its activity increases rapidly with an increase 

 in temperature until 35 C. is reached. From 35 to a 

 little above 60 C. a further but less marked increase is 

 observed. Beyond this point the activity of the ferment 

 falls off rapidly until at 70 C. it acts no more energetically 

 than at about 15. A curve similar to those shown on p. 89 

 would therefore represent graphically the influence of tem- 

 perature upon amylase. 1 



The reaction which amylase catalyzes is incomplete when 

 allowed to take place in glass, the saccharification coming to 

 a standstill when less than half of the total starch present has 

 been converted into maltose. The exact point varies with ex- 

 ternal conditions of temperature, concentration, etc. We shall 

 see* later that this fact indicates that the action of amylase is 

 reversible. Evidence of the truth of this statement has recently 

 been brought by CREMER, 2 who has shown that a ferment 

 (perhaps identical with amylase) which has the power of 

 splitting glycogen (an isomer of starch, and often called 

 animal starch) into glucose is also able to synthesize glycogen 

 from glucose. 



If sufficient time is given, the amount of change brought 

 about in a starch paste is the same, no matter what the 

 concentration of the amylase. 



The activity of amylase is markedly influenced by the 

 presence of different chemical substances in the reaction 

 mixture. Amylase seems to act best in a neutral medium. 



1 See EFFRONT: Die Diastasen. Translated into German by BUCHE- 

 LER, Leipzig, 1900, 1, p. 119. 



2 CREMER: Ergebnissed. Physiol., 1902, 1, Ite Abth., p. 803. 



