Figure 5.

Comparative activity of Xth family endonucleases. Comparison of the 3′-phosphatase and 3′–5′ exonuclease activities of NExo, NApe, E. coli ExoIII and human hAP1. The substrates 50-PO₄ (100 nM; A–C) and 20-OH (200 nM; D) were incubated with different concentrations of enzyme as indicated under standard phosphatase assay conditions. Samples were taken at the time points indicated and the reactions quenched before separation by 20% denaturing PAGE.