Chain-length substrate specificity of WT and mutant ROL toward p-nitrophenyl esters at 35°C in pH 8.0 50 mM Tris-HCl buffer. (A) WT; (B to K) single mutants (L258F, E265A, E265H, E265P, E265W, E265V, E265Y, S267T, S267W, S267Y); (L) double mutant S265V/S267W.