This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
The presence of a noncompetitive inhibitor can be implicated in which of the outcome? 
Select and explain. 
A. Leads to both an increase in the Vmax of a reaction and an increase in the Km, B. Leads to a decrease in the observed Vmax, C. Leads to a decrease in Km and Vmax, D. Leads to an increase in Km without affecting Vmax
B: Leads to a decrease in the observed Vmax
Answer: B: Leads to a decrease in the observed Vmax 
Explanation: In the presence of a noncompetitive inhibitor, Vmax is decreased, whereas Km is unchanged. The steady-state concentration of ES is decreased.