Intrinsic thermodynamics of ethoxzolamide inhibitor binding to human carbonic anhydrase XIII

BMC Biophysics

Table 1 Observed thermodynamic parameters of EZA binding to hCA XIII in phosphate and TRIS buffers are listed as a function of pH as determined by ITC at 25°C

pH	K_{b_obs}, M^-1	Δ_bG_obs, kJ/mol	Δ_bH_obs, kJ/mol	TΔ_bS_obs, kJ/mol	Δ_bS_obs, kJ/(mol × K)
EZA - hCA XIII binding in phosphate buffer
6.0	1.70 × 10⁷	−41.27	−11.36	29.91	0.10
7.0	1.17 × 10⁸	−46.05	−17.84	28.21	0.09
8.0	4.96 × 10⁸	−49.63	−37.76	11.87	0.04
9.0	3.33 × 10⁸	−48.65	−66.48	−17.84	−0.06
EZA - hCA XIII binding in TRIS buffer
6.0	5.95 × 10⁶	−38.67	−58.20	−19.53	−0.07
7.0	2.10 × 10⁸	−47.50	−59.71	−12.20	−0.04
8.0	8.69 × 10⁸	−51.02	−48.79	2.24	0.01
9.0	2.27 × 10⁸	−47.70	−33.36	14.33	0.05

Both the observed binding constants and enthalpies were highly pH and buffer-dependent. Standard deviations are below 10% for all parameters measured in kJ/mol.

ISSN: 2046-1682