TABLE 4.

Phosphorylation by human cytoplasmic TK^a

Compound	Km (μM)	Relative Vmaxd
dThd	2.6b	100
AZT	NDc	55.5 ± 9.7
D4T	133	2.1 ± 0.7
4′-Methyl D4T	ND	1.6 ± 0.5
4′-Vinyl D4T	ND	1.8 ± 0.5
4′-Ethynyl D4T	52	3.8 ± 0.8
4′-Methylethynyl D4T	ND	2.5 ± 0.9
4′-Chloroethynyl D4T	ND	3.9 ± 1.0
4′-Allyl D4T	ND	0.4 ± 0.2
4′-Cyano D4T	ND	1.1 ± 0.2

^aData represent results obtained with 250 μM dThd or an analog and 2.4 mM ATP incubated with 0.07 U of TK-1 at 37°C for 285 min.

^bValue published previously (24).

^cND, not determined.

^dNumbers represent means and standard deviations of at least three separate determinations.