Fig. 5.

Enhancement of TDG steady-state turnover by APE1. (A) Single-turnover experiments, performed with 1.0 μM TDG and 0.3μM G·caC substrate, yield a rate constant of k_obs = 0.50 ±0.02 min⁻¹, reflecting the maximal rate of product formation (k_max). (B) Multiple-turnover experiments performed with 0.05 μM TDG and 1.0 μM G·caC substrate give a slow steady-state rate constant of k_cat = 0.011 ±0.002 min⁻¹ in the absence of APE1 (blue line, circles). Steady-state turnover is much (32-fold) higher for TDG in the presence of 1.2 μM APE1, $k_{\text{cat}}^{+\text{APE}1}=0.35\pm 0.04{min}^{-1}$ (triangles), and approaches the theoretical maximum ( $k_{\text{cat}}^{+\text{APE}1}=0.7k_{max}$).