Carbonic anhydrase inhibitors: purification and inhibition studies of pigeon (Columba livia var. domestica) red blood cell carbonic anhydrase with sulfonamides

Figures & data

Table 1.  Kinetic parameters for CO₂ hydration reaction catalysed by the cytosolic α-CA isozymes of mammalian and avian, origin and their susceptibility to acetazolamide (AZA) inhibition.

Isozyme	Activity level	kcat	kcat/Km	KI (AZA)
		(s^−1)	(M^−1.s^−1)	(nM)
hCA I*	Moderate	2.10^5	5.10^7	250
hCA II*	Very high	1.4.10^6	1.5.10^8	12
hCA III**	Low	1.0.10^4	3.10^5	300,000
scCA***	High	1.2.10^6	1.8.10^7	303
clCA	High	1.3.10^6	1.1.10^8	71

*From refs.^1–3.

**From ref.³⁰.

***From ref.¹⁵.

CA, carbonic anhydrase; cl, pigeon enzyme; h, human; m, murine; sc, ostrich isozymes.

Figure 1.  SDS PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) for clCA purified from red blood cells (lane 4) compared to ladder (lane 1). hCA I (lane 2) and hCA II (lane 3). The hCAs were from Sigma–Aldrich.

Table 2.  hCA II, scCA, and clCA inhibition data with sulfonamides 1–5, acetazolamide (AZA), ethoxzolamide (EZA) and sulfanilamide (SA). Data of hCA II and scCA are from refs.^15,21–27.

No	n	R	KI (nM)
			hCA II^a	scCA^b	clCA^c*
1a	0	CH3CO	246	4550	467 ± 12
1b	0	CF3CO	133	4700	325 ± 14
1c	0	EtCO	232	3600	382 ± 21
1d	0	n-PrCO	227	397	355 ± 16
1e	0	i-PrCO	258	573	369 ± 20
1f	0	n-BuCO	214	260	360 ± 17
1g	0	t-BuCO	230	540	147 ± 8
1h	0	PhCO	37	3245	95 ± 6
1i	0	MeSO2	64	66	137 ± 12
1j	0	PhSO2	49	2430	41 ± 3
1k	0	4-AcNHC6H4 SO2	82	2600	36 ± 3
1m	1	PhSO2	40	318	31 ± 2
1n	1	PhNH-C(=S)	12	2970	679 ± 48
1p	2	PhNH-C(=S)	53	2980	621 ± 31
1q	2	PhNH-C(=O)	75	39	238 ± 12
1r	2	4-H2NO2SC6H4NH-C(=S)	4	3030	16 ± 1
1s	2	4-H2NO2SC6H4CO	5	25	15 ± 0.8
2	—	PhNH-C(=O)	150	3650	156 ± 10
3	—	PhNH-C(=O)	100	69	79 ± 7
4a	—	4-BrC6H4SO2	2	62	1.9 ± 0.2
4b	—	4-O2NC6H4SO2	1	72	3.5 ± 0.3
5	—	Furan-2-yl-CO	6	768	3.6 ± 0.2
AZA	—	—	12	303	71 ± 6
EZA	—	—	8	3.9	12 ± 1
SA	—	—	300	570	3460 ± 68

*Mean ± standard error (from three assays).

^aHuman, recombinant enzyme, data from ref.^21–27.

^bStruthio camelus red blood cell enzyme, data from ref.¹⁵.

^cColumba livia red blood cells enzyme, this study.

Nishimori I, Minakuchi T, Onishi S, Vullo D, Cecchi A, Scozzafava A et al. Carbonic anhydrase inhibitors: cloning, characterization, and inhibition studies of the cytosolic isozyme III with sulfonamides. Bioorg Med Chem 2007;15:7229–7236.

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Ozensoy O, Isik S, Arslan O, Arslan M, Scozzafava A, Supuran CT. Carbonic anhydrase inhibitors. Inhibition of red blood cell ostrich (Struthio camelus) carbonic anhydrase with a series of aromatic and heterocyclic sulfonamides. J Enzyme Inhib Med Chem 2005;20:383–387.

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