Figure 1. Relative activities of the mutants identified after screening.

For each variant the relative activity at Aβ divided by the relative activity on the off target peptides is shown in the black bar and the relative activity at Aβ is shown in the open bar. Mutants are ranked by relative activity at Aβ divided by the relative activity on the off target peptides after the first (A) and second (B) rounds of screening. Each bar represents and average of four readings for each variant on Aβ alone, or Aβ and up to 9 other peptides. Error bars are not shown due to the complex nature of the propagation of errors calculation for the relative specificity change where activity on up to 11 different peptides was measured for both wild-type and variant enzymes. For the first round of screening only the top 50 mutants are shown. Despite the intention of introducing only single amino acid substitutions into the enzyme in the first round a number of the variants with improved specificity had acquired two mutations. Activities are relative to the wild-type enzyme.