Sulphonamide inhibition studies of the β-carbonic anhydrase GsaCAβ present in the salmon platyhelminth parasite Gyrodactylus salaris

Figures & data

Figure 1. Sulphonamides/sulfamates 1–24 and AAZ-HCT investigated as inhibitors in the present study.

Table 1. Kinetic parameters for the CO₂ hydration reaction catalysed by α- and β-class CA enzymes: the human cytosolic isozymes hCA I and II (α-class) at 20 °C and pH 7.5 in 10 mM HEPES buffer, and GsaCAβ (measured at 20 °C, pH 8.3 in 20 mM TRIS buffer and 10 mM NaClO₄) are shown. Inhibition data with the clinically used sulphonamide acetazolamide are also presented.

Isozyme	Activity level	kcat	kcat/Km	KI (acetazolamide)
		(s^−1)	(M^−1 × s^−1)	(nM)
hCA I^a	Moderate	2.0 × 10^5	5.0 × 10^7	250
hCA II^a	Very high	1.4 × 10^6	1.5 × 10^8	12
GsaCAβ^b	Low-moderate	1.1 × 10^5	7.58 × 10^6	460.5

^aFrom ref. [12,15]; ^bFrom ref. [1].

Table 2. Inhibition of β-CA from G. salaris and human isoforms hCA I and hCA II with sulphonamides 1–24 and the clinically used drugs AAZ-HCT, by a stopped-flow assay²⁶.

	KI (nM)^a
Inhibitor	hCA I	hCA II	GsaCAβ
1	28,000	300	522.8
2	25,000	240	589.2
3	79	8	388.8
4	78,500	320	3115
5	25,000	170	2144
6	21,000	160	7790
7	8300	60	854.4
8	9800	110	7266
9	6500	40	8879
10	7300	54	9103
11	5800	63	16900
12	8400	75	24820
13	8600	60	81.9
14	9300	19	139.7
15	5500	80	419.8
16	9500	94	616.1
17	21,000	125	917.4
18	164	46	687.6
19	109	33	489.1
20	6	2	631.8
21	69	11	5839
22	164	46	765.9
23	109	33	653.2
24	95	30	382.2
AAZ	250	12	460.5
MZA	50	14	721.7
EZA	25	8	545.9
DCP	1200	38	3261
DZA	50,000	9	399.1
BRZ	45,000	3	5063
BZA	15	9	716.3
TPM	250	10	8558
ZNS	56	35	8576
SLP	1200	40	7288
IND	31	15	7423
VLX	54,000	43	3892
CLX	50,000	21	4621
SLT	374	9	877.1
SAC	18,540	5959	1635
HCT	328	290	776.8

^aMean from three different assays. Errors (data not shown) were in the range of ± 10% of the reported data.

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