Carbonic anhydrase IV (CA4) anchored to extracellular face of the plasma membrane (Wistrand et al. 1999) hydrates carbon dioxide (CO2) to yield bicarbonate (HCO3-) and a proton (H+) (Zhu & Sly 1990, Okayuma et al. 1992, Baird et al. 1997, Innocenti et al. 2004). During the reaction a hydroxyl group bound by the zinc ion (Zn2+) of CA4 attacks the CO2 molecule to directly form HCO3- (reviewed in Lindskog 1997). The HCO3- is displaced by water, which is then deprotonated by a histidine residue to recreate the Zn2+:hydroxyl group. Depending on the concentrations of reactants the reaction is reversible.
Sly, WS, Fierke, CA, Okuyama, T, Baird TT, Jr, Waheed, A
Sly, WS, Zhu, XL
Innocenti, A, Wurl, M, Supuran, CT, Scozzafava, A, Antel, J, Firnges, MA
Sly, WS, Sato, S, Okuyama, T, Waheed, A, Zhu, XL
Carter, ND, Wistrand, PJ, Conroy, CW, Mahieu, I
Lindskog, S
carbonate dehydratase activity of CA4:Zn2+ [plasma membrane]
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