Time course uracil excision by UDGs. Excision of uracil from a double-stranded DNA oligomer, AU9, by wild-type (triangles), Y66F (squares), Y66H (crosses), Y66L (diamonds) and Y66W (circles) UDGs. Reactions using appropriate dilutions (Materials and Methods) were carried out such that 30–50% of substrate was converted to product. The amount of product formed was calculated as pmoles of uracil released per microgram of UDG and plotted against time.