| Carbonic anhydrase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 | |||||||||
| Identifiers | |||||||||
| EC no. | 4.2.1.1 | ||||||||
| CAS no. | 9001-03-0 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
| |||||||||
| Eukaryotic-type carbonic anhydrase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Carb_anhydrase | ||||||||
| Pfam | PF00194 | ||||||||
| InterPro | IPR001148 | ||||||||
| PROSITE | PDOC00146 | ||||||||
| SCOP2 | 1can / SCOPe / SUPFAM | ||||||||
| Membranome | 333 | ||||||||
| |||||||||
The carbonic anhydrases (or carbonate dehydratases) (EC 4.2.1.1) form a family of enzymes that catalyze the interconversion between carbon dioxide and water and the dissociated ions of carbonic acid (i.e. bicarbonate and hydrogen ions).[1] The active site of most carbonic anhydrases contains a zinc ion. They are therefore classified as metalloenzymes. The enzyme maintains acid-base balance and helps transport carbon dioxide.[2]
Carbonic anhydrase helps maintain acid–base homeostasis, regulate pH, and fluid balance. Depending on its location, the role of the enzyme changes slightly. For example, carbonic anhydrase produces acid in the stomach lining. In the kidney, the control of bicarbonate ions influences the water content of the cell. The control of bicarbonate ions also influences the water content in the eyes. Inhibitors of carbonic anhydrase are used to treat glaucoma, the excessive build-up of water in the eyes. Blocking this enzyme shifts the fluid balance in the eyes to reduce fluid build-up thereby relieving pressure.[2][3]
Carbonic anhydrase is critical to hemoglobin function via the Bohr effect which catalyzes the hydration of carbon dioxide to form carbonic acid and rapidly dissociate into water.[4] Essentially an increase in carbon dioxide results in lowered blood pH, which lowers oxygen-hemoglobin binding.[5] The opposite is true where a decrease in the concentration of carbon dioxide raises the blood pH which raises the rate of oxygen-hemoglobin binding. Relating the Bohr effect to carbonic anhydrase is simple: carbonic anhydrase speeds up the reaction of carbon dioxide reacting with water to produce hydrogen ions (protons) and bicarbonate ions.
To describe equilibrium in the carbonic anhydrase reaction, Le Chatelier's principle is used. Most tissue is more acidic than lung tissue because carbon dioxide is produced by cellular respiration in these tissues, where it reacts with water to produce protons and bicarbonate. Because the carbon dioxide concentration is higher, the equilibrium shifts to the right, to the bicarbonate side. The opposite is seen in the lungs, where carbon dioxide is being released, reducing its concentration, so the equilibrium shifts to the left, favoring carbon dioxide production.[6]
- ^ Badger MR, Price GD (1994). "The role of carbonic anhydrase in photosynthesis". Annu. Rev. Plant Physiol. Plant Mol. Biol. 45: 369–392. doi:10.1146/annurev.pp.45.060194.002101.
- ^ a b "PDB101: Molecule of the Month: Carbonic Anhydrase". RCSB: PDB-101. Retrieved 3 December 2018.
- ^ Supuran CT (27 May 2004). "Carbonic Anhydrases: Catalytic and Inhibition Mechanisms, Distribution and Physiological Roles". In Supuran CT, Scozzafava A, Conway J (eds.). Carbonic Anhydrases. Taylor & Francis. doi:10.1201/9780203475300. ISBN 9780203475300. Archived from the original on 11 April 2023. Retrieved 19 July 2022.
- ^ Occhipinti R, Boron WF (August 2019). "Role of Carbonic Anhydrases and Inhibitors in Acid-Base Physiology: Insights from Mathematical Modeling". International Journal of Molecular Sciences. 20 (15): 3841. doi:10.3390/ijms20153841. PMC 6695913. PMID 31390837.
- ^ "Bohr Effect". www.pathwaymedicine.org. Retrieved 23 November 2019.
- ^ "Le Chatelier's Principle". www.chemguide.co.uk. Retrieved 23 November 2019.