Table 3.

Effects of dC-flanking sequences of the substrate on kinetic parameters of Endo IV

Oligonucleotide	Km (μM)	Relative Km	kcat (min−1)	Relative kcat	kcat/Km (μM−1 min−1)	Relative kcat/Km
5′-(dA)7dAdAdCdAdA(dA)7-3′	23	1.0	0.34	1.0	0.015	1.0
5′-(dA)7dAdTdCdAdA(dA)7-3′	18	0.78	1.0	2.9	0.056	3.7
5′-(dA)8dGdTdCdAdG(dA)8-3′	17	0.74	0.52	1.5	0.031	2.1

The activity of Endo IV was determined by measurement of the amount of acid-soluble nucleotides released from the substrate. Kinetic parameters were determined by a least-squares fit of the data in Lineweaver–Burk plots. The relative K_m, relative k_cat and relative k_cat/K_m were calculated by dividing the K_m, k_cat and k_cat/K_m values for each substrate by those for 5′-(dA)₇dAdAdCdAdA(dA)₇-3′. Data are means from two independent experiments.