(a) hFEN1-catalyzed reaction schematic showing double nucleotide unpairing at
positions +1 and ā1 (numbering relative to scissile phosphate). (b,c)
Reaction schemes of mixed inhibition (b) and competitive inhibition (c) models.
In each case, E, S, I and P represent enzyme, substrate, inhibitor and product,
respectively. Kic is the dissociation constant of I
from free enzyme (competitive with substrate) and
Kiu is the dissociation constant of I from ES
complex (uncompetitive). (dāf) Nonlinear regression plots of normalized
initial rates of reaction vs. substrate concentration (open diamonds) for
substrate DF1 at varying concentrations of compounds 1 (d; inset
shows equation for mixed inhibition model), 2 (e; inset shows
legend correlating color/symbol to inhibitor concentration) and 4
(f; inset shows equation for competitive inhibition model). Error bars represent
standard errors from global fitting of combined data from two triplicate
experiments (fits to alternative models are shown in Supplementary Figures
S7āS9).