An enzyme was reacted with a site specific inhibitor for a few minutes and then
ID: 198738 • Letter: A
Question
An enzyme was reacted with a site specific inhibitor for a few minutes and then assayed for activity. The Vmax of the enzyme was reduced from 100 umol/min to 20 umol/min. The inhibitory reaction was repeated using the same amount of inhibitor under the same conditions, except that a 5 mM concentration of the enzyme’s substrate was present in the reaction mixture. Under these revised conditions the Vmax of the enzyme was reduced to 50 umol/min. Offer some explanations as to why there was less inhibition when the enzyme’s substrate was present in the reaction mixture.
There is less inhibition when there is more substrate present because when there a competitive inhibitor present, adding more substrate will increase the chances of the substrate binding to the active site rather the competitive inhibitor bind to the active site.
Explanation / Answer
There is less inhibition when the enzyme's substrate was present in the reaction mixture because of increasing concentration of enzymes substrate in presence of competitive inhibitor more substrate will bind to the active site of the enzymes rather than the inhibitory molecule. Hence, the Vmax of the enzyme was reduced to 50 umol/min from 100 umol/min.