. 2014 May 1;136(21):7643–7654. doi: 10.1021/ja413174b

Table 1. pK_a Values for Inactivation at Low pH for Semisynthetic KSI Tyr16 Variants from pH Dependencies of Activity with Subsaturating (pK_a^E,1) and Saturating (pK_a^E·S,1) 5(10)-EST^a.

residue at position 16	side chain solution pK_a^b	pK_a^E,1 (subsaturating)	pK_a^E·S,1 (saturating)
Tyr (WT)	9.95	4.31 ± 0.05	4.28 ± 0.11
2-F-Tyr	9.28	4.35 ± 0.10	4.24 ± 0.07
3-F-Tyr	8.81	4.30 ± 0.07	4.52 ± 0.09
2,6-F₂-Tyr	8.35	4.29 ± 0.05	4.18 ± 0.06
3-Cl-Tyr	8.48	4.17 ± 0.12	4.35 ± 0.06

Values are from fits to data in Figure S3 (Supporting Information) and are shown together with standard errors from regression analysis.

The side chain solution pK_a values are for the corresponding phenols.^86,87

Table 1. pKa Values for Inactivation at Low pH for Semisynthetic KSI Tyr16 Variants from pH Dependencies of Activity with Subsaturating (pKaE,1) and Saturating (pKaE·S,1) 5(10)-ESTa.