Structural annotation of human carbonic anhydrases

Figures & data

Table 1.  Catalytic efficiency and distribution of hCA isoforms.

Isoform	kcat (s^−1)	KM (mM)	kcat/KM (M^−1 s^−1)	Localization		Ref
				Sub-cellular	Tissue/Organ
hCA I	2.0 × 10^5	4.0	5.0 × 10^7	Cytosol	RBCs, GI tract	^Citation5,Citation9,Citation95
hCA II	1.4 × 10^6	9.3	1.5 × 10^8	Cytosol	RBCs, GI tract, eyes, Osteoclasts, kidneys, lungs, testes, brain	^Citation5,Citation9,Citation95
hCA III	1.0 × 10^4	33.3	3.0 × 10^5	Cytosol	Skeletal muscles, adipocytes	^Citation5,Citation9,Citation95
hCA IV	1.1 × 10^6	21.5	5.1 × 10^7	Membrane-bound	Kidneys, lungs, pancreas, brain, capillaries, colon, heart muscles	^Citation5,Citation9
hCA VA	2.9 × 10^5	10.0	2.9 × 10^7	Mitochondria	Liver	^Citation12
hCA VB	9.5 × 10^5	9.7	9.8 × 10^7	Mitochondria	Heart and skeletal muscles, pancreas, kidneys, GI tract, spinal cord	^Citation12
hCA VI	3.4 × 10^5	6.9	4.9 × 10^7	Secretory (milk/saliva)	Salivary and mammary glands	^Citation13
hCA VII	9.5 × 10^5	11.4	8.3 × 10^7	Cytosol	CNS	^Citation14
hCA-RP VIII	–			Cytosol	CNS	^Citation5,Citation9,Citation95
hCA IX	3.8 × 10^5	6.9	5.5 × 10^7	Transmembrane	Tumours, GI mucosa	^Citation95,Citation96
hCA-RP X	–			Cytosol	CNS	^Citation5,Citation9,Citation95
hCA-RP XI	–			Cytosol	CNS	^Citation5,Citation9,Citation95
hCA XII	4.2 × 10^5	12.0	3.5 × 10^7	Transmembrane	Renal, intestinal, reproductive epithelia, eye, tumours	^Citation89
hCA XIII	1.5 × 10^5	13.8	1.1 × 10^7	Cytosol	Kidneys, brain, lungs, gut, reproductive tract	^Citation18
hCA XIV	3.1 × 10^5	7.9	3.9 × 10^7	Transmembrane	Kidneys, brain, liver	^Citation90

Table 2.  Primary sequence identity (upper right) and number of conserved residues (lower left) among hCA isoforms.

	I	II	III	IV	V	VI	VII	IX	XII	XIV
I	-	60.5	54.4	28.8	43.7	30.9	50.6	31.3	29.8	32.6
II	158	-	58.9	32.4	49.4	32.5	55.9	31.4	28.4	36.0
III	142	153	-	30.2	43.3	32.8	52.9	29.5	27.3	33.0
IV	78	88	82	-	27.9	31.3	33.1	29.4	26.0	34.2
V*	114	129	113	76	-	28.6	47.9	29.0	24.3	32.6
VI	83	87	88	85	77	-	35.3	41.0	35.4	41.4
VII	132	146	138	90	125	95	-	34.6	31.6	36.3
IX	85	85	80	80	79	110	94	-	31.2	41.9
XII	79	75	72	70	64	93	84	83	-	37.8
XIV	86	82	88	93	87	110	97	113	99	-

*Murine CA.

Table 3.  Structural main chain r.m.s.d. (Å) among hCA isoforms.

	I	II	III	IV	V*	VI	VII	IX	XII	XIII	XIV
I	-	0.98	0.87	2.48	1.02	1.55	0.99	2.02	2.07	0.85	1.52
II		-	0.96	2.29	0.98	1.48	0.77	2.05	2.17	0.76	1.50
III			-	2.37	1.01	1.69	0.86	1.79	1.99	0.85	1.41
IV				-	1.65	1.52	2.36	2.81	2.78	1.39	2.48
V*					-	1.47	0.83	1.82	1.89	1.30	1.42
VI						-	1.52	1.35	1.58	1.58	1.49
VII							-	1.79	1.97	0.77	1.42
IX								-	1.87	2.06	1.88
XII									-	1.17	1.86
XIII										-	1.18
XIV*											-

*Murine CA.

Figure 1.  Multiple sequence alignment of the hCA isoforms. Gradients of blue represent sequence conservation from most (dark blue) to least conserved (light blue).

Figure 2.  (A) Cartoon representation of superposition of the 11 catalytic isoforms of α-CA, in shades of blue. The histidines (94, 96 and 119) that coordinate the Zn²⁺ are shown as yellow sticks. (B) Worm representation of main chain r.m.s.d. of the 11 catalytic isoforms. Thicker regions represent more deviation in the main chain. Active site Zn²⁺ is represented as a magenta sphere. Figure was made using Chimera¹¹⁰.

Figure 3.  Stick representation of the active site of hCA II (PDB ID 3D92)² showing key residues that are involved in CO₂ binding and proton transfer during catalysis. Residues are as labelled. Active site Zn²⁺ is shown as a magenta sphere and water molecules involved in proton transfer are shown as red spheres.

Figure 4.  Surface representation of conservation of hydrophobic amino acids among the catalytic α-CAs. The conserved residues are coloured in a gradient of dark (most conserved) to light (least conserved) green. Active site Zn²⁺ is shown as a magenta sphere. Figure was made using Chimera¹¹⁰.

Figure 5.  Surface representation of conservation of hydrophilic amino acids among the catalytic α-CAs. The conserved residues are coloured in a gradient of red (negatively charged) and blue (positively charged), from dark (most conserved) to light (least conserved). Active site Zn²⁺ is shown as a magenta sphere. Figure was made using Chimera¹¹⁰.

Table 4.  Reactions that CAs are believed to be involved in³.

O=C=O + H2O ↔ HCO3^− + H^+

O=C=NH + H2O ↔ H2NCOOH

HN=C=NH + H2O ↔ H2NCONH2

RCHO + H2O ↔ RCH(OH)2

RCOOAr + H2O ↔ RCOOH + ArOH

RSO3Ar + H2O ↔ RSO3H + ArOH

ArF + H2O ↔ HF + ArOH

Ar = 2,4 – dinitrophenyl

PhCH2OCOCl + H2O ↔ PhCH2OH + CO2 + HCl

RSO2Cl + H2O ↔ RSO3H + HCl

R = Methyl or Phenyl (Ph)

Figure 6.  Stereo cartoon-surface representation of hCA II (gray) showing the analogous positions of cysteines (green) present in all the catalytic hCAs. Active site Zn²⁺ is shown as a magenta sphere.

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