Anion inhibition studies of the α-carbonic anhydrases from Neisseria gonorrhoeae

Figures & data

Figure 1. Active site view of A. hCA II (pdb 1RAY) and B. NgCA (pdb 1KOP) in adduct with the azide anion N₃^-. Amino acid residues of NgCA are renumbered according to the corresponding residues from hCA II. The zinc ion, represented as a grey sphere, is coordinated by three His residues, that are His94, His96 and His119, and the azide anion. Residues constituting the α-helix portion 128–139 are coloured magenta in hCA II, while being absent in NgCA.

Table 1. Inhibition constants (K_Is) of anion inhibitors against hCA I, II and NgCA by a stopped flow CO₂ hydration assay¹⁷.

	KI (mM)^a
Anion^b	hCA I	hCA II	NgCA
F^−	>300	>300	8.3
Cl^−	6	200	4.8
Br^−	4	63	4.0
I^−	0.3	26	9.6
NCO^−	0.0007	0.03	0.43
NCS^−	0.2	1.6	0.92
CN^−	0.0005	0.02	1.0
N3^−	0.0012	1.51	2.1
NO2^−	8.4	63	0.59
NO3^−	7	35	0.85
HCO3^−	12	85	1.3
CO3^2-	15	73	2.9
HSO3^−	18	89	0.66
SO4^2-	63	>200	0.83
HS^−	0.0006	0.04	0.55
NH2SO2NH2	0.31	1.13	0.058
NH2SO3H	0.021	0.39	0.024
PhAsO3H2	31.7	49	0.74
PhB(OH)2	58.6	23	0.15
ClO4^−	>200	>200	>100
SnO3^2-	0.57	0.83	1.7
SeO4^2-	118	112	0.87
TeO4^2-	0.66	0.92	0.76
OsO5^2-	0.92	0.95	2.3
P2O7^2-	25.8	48	4.9
V2O7^2-	0.54	0.57	2.8
B4O7^2-	0.64	0.95	0.65
ReO4^−	0.11	0.75	0.96
RuO4^−	0.101	0.69	1.9
S2O8^2-	0.107	0.084	0.79
SeCN^−	0.085	0.086	0.66
NH(SO3)2^2-	0.31	0.76	0.25
FSO3^−	0.79	0.46	0.61
CS3^2-	0.0087	0.0088	0.088
EtNCS2^−	0.00079	0.0031	0.0051
PF6^−	>100	>100	>100
CF3SO3^−	>100	>100	5.7

^a Mean from 3 different assays, by a stopped flow technique (errors were in the range of ±5–10% of the reported values).

^b As sodium salts, except sulfamide and phenylboronic acid. Phenylarsonic acid and sulphamic acid were also used as disodium and monosodium salts, respectively.

Khalifah RG. The carbon dioxide hydration activity of carbonic anhydrase. I. Stop-flow kinetic studies on the native human isoenzymes B and C. J Biol Chem 1971;246:2561–73.

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