Table 2.

Kinetic parameters for the CO2 hydration reaction catalyzed by various CAs

Isozyme	Activity level	kcat (s-1)	kcat/Km (M-1s-1)	KI (nM)c
HCA Ia	moderate	2.0 × 105	5.0 × 107	250
HCA IIa	very high	1.4 × 106	1.5 × 108	12
Can2a	moderate	3.9 × 105	4.3 × 107	10.5
Nce103a	high	8.0 × 105	9.7 × 107	132
ScCAa	high	9.4 × 105	9.8 × 107	82
CgCAa	moderate	3.8 × 105	4.8 × 107	11
DmBCAb	high	9.5 × 105	1.1 × 108	49

Kinetic parameters for the human cytosolic isozymes human HCA I and II (α-class CAs) at 20°C and pH 7.5 in 10 mM HEPES buffer and 20 mM Na₂SO₄, in addition to the β-CAs Can2, Nce103 (from C. neoformans and C. albicans, respectively), ScCA (from S. cerevisiae), CgCA (from C. glabrata) and DmBCA (from Drosophila melanogaster) measured at 20°C, pH 8.3 in 20 mM Tris buffer and 20 mM NaClO₄ are shown. Inhibition data with the clinically used sulfonamide acetazolamide (5-acetamido-1,3,4-thiadiazole-2-sulfonamide) are also provided.

^aReference [30]

^bThis work

^cacetazolamide