The Ki of novel competitive inhibitor designed against an

The K_i of novel competitive inhibitor designed against an enzyme is 2.5 µM. The enzyme was assayed in the absence or presence of the inhibitor (5 µM) under identical conditions. The K_m in the presence of the inhibitor was found to be 30 µM. The Km in the absence of the inhibitor is ____ µM.

	1	=	K_m		1	+	1	.......(1)
	V		[S]		V_max		V_m1

K_m1

1 +

.......(2)

V_max

[S]

V_min

Then equation (1) – (2) and by simplification

K_m = 30		1 +	5		= 90
			2.5

Note : If we take K_m in the absence of the inhibitor 30 µM then K_m in the presence of the inhibitor can be calculated as per above formulae 10 µM.