Table 3. S_p-dNTPαS Inhibition of SAMHD1 R_p-dNTPαS Hydrolysis.

substrate	Sp-dNTPαS	kcat (s–1)	fold reductionb
Rp-dATPαS		0.33 ± 0.01a	1.7
Rp-dATPαS	Sp-dATPαS	0.20 ± 0.01
Rp-dGTPαS		0.192 ± 0.001	7.1
Rp-dGTPαS	Sp-dGTPαS	0.027 ± 0.001
Rp-TTPαS		0.885 ± 0.001	4.9
Rp-TTPαS	Sp-TTPαS	0.181 ± 0.004
Rp-dCTPαS		0.199 ± 0.004	7.7
Rp-dCTPαS	Sp-dCTPαS	0.026 ± 0.006

^aError is the SEM derived of at least two independent measurements.

^bFold reduction is the ratio of k_cat for hydrolysis of each R_p-dNTPαS diastereomer in the absence or presence of the S_p-dNTP diastereomer.