Question

An enzyme catalyzed reaction was performed in the presence and in the absence of an inhibitor. The Lineweaver Burk plot showed competitive kinetics with x-intercepts of -10mm -1 and -3.5mm -1 in the presence and absence of the inhibitor respectively. If the inhibitor concentration used was 2micro molar (UM), calculate KI for the inhibitor enzyme binding? a. none of the above b. 0.135nM c. 0.054nM d. 0.225nM e. 1077 nM

Answer 1

Answer-

According to the given question-

Here we have an enzyme-catalyzed, reaction observed in presence as well as the absence of inhibitor, and in the Lineweaver Burk plot, we have observed that-

1 $\div$ Km = 10 ,

Km = 0.1

1 $\div$ $\alpha$Km = 3.5

$\alpha$Km = 0.2857

Km $\div$ $\alpha$Km = 0. 1 $\div$ 0.2857

1 $\div$ $\alpha$ = 0.35

$\alpha$ = 1 $\div$ 0.35 = 2.857

$\alpha$ = 1 + [I] $\div$ KI

2.857 = 1 + (0.002) $\div$ KI

2.857 KI = KI + 0.002

2.857 KI - KI = 0.002

1.857 KI = 0.002

KI = 0.001077 mM

KI = 1077nM

Thus the correct answer is (E) KI = 1077nM