EFFECTS OF TEMPERATURE: ENZYMES 



763 



Despite the fact that the inhibition is noncomiietitive, the inhibition will 

 depend on the substrate concentration, but in a different manner than in 

 competitive inhibition since here the inhibition will be increased as the 

 substrate concentration rises. As K approaches infinity, the inhibition 

 becomes classically noncompetitive. The inhibition will again decrease as 

 the temperature is increased. 



Case IV: inhibitor combines ivith both E^ and E^^ — competitive 



A- E„S -> E„ + P 



A'/ K 



EJ ;^ Ed ;^ Efl 



A', EJ 



(15-27) 



The rate and inhibition equations are somewhat more complex than in 

 the previous situations: 



^™^^^ (15-28) 



(S) + K, 



1 + 



1 



(I) 



if, 



+ 



(I) 



KK/ 



(I) + 



KKjKi' 



K, + KK/ 



2_ , i^ 



K + K, 



(15-29; 



These more general equations reduce to 15-19 and 15-20 when K^ = oo, 

 and to Eqs. 15-22 and 15-23 when K/ = oo, as expected. The variation of 

 the inhibition with temperature will be complex and will depend on the 

 relative values of K, and K/. 



Case V: inhibitor combines with both E^ and E^^ — noncompetitive 



Ea+P 



(15-30) 



K, E,S A', 

 A'/ K ^ ■^ 



E J — E, — E„ E,SI 



A-,. 



EJ 



If an enzyme can exist in active and inactive forms, this situation is prob- 

 ably fairly common and leads to the following rate and inhibition equa- 

 tions: 



VJQ) 



Vi = 



K Ki KK/ 



(I) + K, 



(S) + K,[l + aiK)] 



,(S) + K,[l + {K.jKK/)] 



(15-31) 



(15-32) 



