Saccharin Sulfonamides as Inhibitors of Carbonic Anhydrases I, II, VII, XII, and XIII

Table 2

Compound dissociation constants of human recombinant CA isoforms I, II, VII, XII, and XIII, as determined by ITC (37°C, pH 7.0). Acetazolamide (AZM) was used as a control. The affinity range of ITC determinations is quite narrow. At our experimental conditions, 5–10 M CA in the calorimeter cell, the range may cover 1000–50 nM affinities (for the Wiseman factor of 100 to 10). With some approximation, the range could be expanded to cover affinities of 100 µM to 20 nM. These ITC measurements essentially confirm the FTSA results.

Compound	Dissociation constants (nM) and CA isoforms
	CA I	CA II	CA VII	CA XII	CA XIII
1	>100,000	>100,000	>100,000	>100,000	>100,000
2	1400	290	560	99	120
3	28	56	160	250	47
4	<20	<20	<20	40	<20
AZM	810	46	63	130	60

Uncertainties of the ITC measurements are approximately 2.0-fold in .