Table 2. Promiscuity Index (I) and Weighted Promiscuity Index (J) for the Round-18 Polymerase.

substrate	CID	kA (M–1min–1)a	kC (M–1min–1)a	kG (M–1min–1)a	kU (M–1min–1)a
ATP	5957	0.30	0.057	0.023	5.3
CTP	6176	0.02	0.008	5.4	0.0002
GTP	135 398 633	0.02	41	0.003	0.23
UTP	6133	87	0.004	0.46	0.001
	fidelity	0.991	0.9996	0.957	0.921
	I	0.020	0.010	0.219	0.126
	J	0.020	0.010	0.220	0.125

^aRate constants (k_N, for N = A, C, G, U) are from Johnston et al.¹¹⁷