Linkage graph showing the k_cat/K_m values of hydrolysis of WT A1-A2-A3 (•), p. R1306 W(○) WT A1-A2 (□) isolated A2 domain (•), and A2-A3 domains (▿). The continuous lines were drawn to eq 4 with the best - fit parameter values k⁺ = 7.26 ± 0.2 × 10⁴ M⁻¹ sec⁻¹ k^CI = 1.23 ± 0.3 × 10⁴M⁻¹ sec ⁻¹, K_d = 35 ± 5 mM (WT A1-A2-A3); k⁺ = 1.36 ± 0.1 × 10⁵ M⁻¹ sec ⁻¹ k^CI = 3 ± 0.5 × 10⁴ M⁻¹ sec⁻¹ , k_d = 158 ± 20 mM (p R1306W), k⁺ 7.47 ± 0.3 × 10⁴ M⁻¹ sec⁻¹ k^CI = 1.38 ± 0.3 × 10⁴ M⁻¹ sec⁻¹, K_d = 36.2 ± 8 mM(A1-A2). No significative NaCl effect was observed for both isolated A2 and A2 -A3 domains