TABLE 2.

Substrate inhibition and feedback inhibition of l-FMAU phosphorylation by cellular kinases^a

Enzyme	Ki (μM)		IC50 (μM)b
	dThd	dCyd	TTP	dCTP
Cytosolic dThd kinase	7 ± 0.1	NDc	4 ± 1	ND
Cytosolic dCyd kinase	ND	1.2 ± 0.1	ND	0.8 ± 0.5
Mitochondrial dPyd kinase	10.8 ± 2	>100	12 ± 2	6 ± 0.1

^aThe values presented here are the averages of triplicate experiments. K_i was determined by using the equation for a competitive inhibitor. 

^bIC₅₀, concentration required for 50% inhibition of l-FMAU phosphorylation. 

^cND, not detectable.