Table 2. Michaelis-Menten Analysis of Dicer-2 incubated with a 515 bp dsRNA and ATP.

The initial rates of converting dsRNA into siRNA for increasing amounts of substrate were measured at saturating ATP (1 mM), and the initial rates of hydrolysis of ATP to ADP were measured at saturating dsRNA (150 nM) for increasing amounts of ATP. The table reports mean ± standard deviation for four trials. Different preparations of Dicer-2 were used here and in Table 1.

	KM(nM)	Vmax(nM min−1)	[ET] (nM)	kcat(min−1)	kcat/KM(nM−1 min−1)
Substrate consumed	6 ± 2	0.2 ± 0.1	1.2	0.2 ± 0.1	0.03 ± 0.02
siRNA produced	6 ± 2	5 ± 2	1.2	4 ± 1	0.7 ± 0.4
ATP hydrolyzed	14,000 ± 4,000	460 ± 70	5	93 ± 14	0.007 ± 0.002