![]() ![]() Ĭarbonic anhydrase is a very ancient enzyme found in both domains of prokaryotes that exists in six different classes among most of the living organisms. Also, it helps the carbon dioxide transport from the lung tissue to the alveoli in the pulmonary capillary, where the carbon dioxide will be excreted during exhalation. ![]() Therefore, carbonic anhydrase helps with the H+ secretion into the lumen of the kidney renal tubule and the reabsorption of HCO 3 - in the kidneys. Since HCO 3 - and H + are regulated in the kidneys and plasma carbon dioxide is regulated in the lungs, both actions in the kidneys and lungs are important to maintain the stability of blood pH. The HCO 3 - and H + are ideal for buffering pH in the blood and tissues because the pKa is close to the physiological pH = 7.2 – 7.6. The HCO 3 - is a conjugate base that neutralizes acids, and the H + is a conjugate acid that neutralizes bases by Acid-base homeostasis. The equilibrium reaction is influenced by the proportion of bicarbonate and H + to carbon dioxide. Regulation of pH Ĭarbonic anhydrase plays an essential role in regulating the blood pH, which speeds up the CO 2 + H 2O ↽ − − ⇀ HCO 3 -+ H + reaction to ensure the equilibrium balance is rapidly maintained. Occurrence and function Ĭarbonic anhydrase was initially found in the red blood cells of cows in 1933 and was simultaneously discovered by Rougton in Cambridge and Meldrum in Philadelphia who were searching for a catalytic factor. The opposite is seen in the lungs, where carbon dioxide is being released so its concentration is lower so equilibrium shifts to the left towards carbon dioxide to try to raise its concentration. ![]() Because the carbon dioxide concentration is higher, equilibrium shifts to the right, to the bicarbonate side. The tissues are more acidic than the lungs because carbon dioxide is produced by cellular respiration and it reacts with water in the tissues to produce the hydrogen protons. To describe equilibrium in the carbonic anhydrase reaction, Le Chatelier's principle is used. 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. 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. Essentially an increase in carbon dioxide results in lowered blood pH, which lowers oxygen-hemoglobin binding. Ĭarbonic 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. Blocking this enzyme shifts the fluid balance in the eyes to reduce fluid build-up thereby relieving pressure. Inhibitors of carbonic anhydrase are used to treat glaucoma, the excessive build-up of water in the eyes. The control of bicarbonate ions also influences the water content in the eyes. In the kidney, the control of bicarbonate ions influences the water content of the cell. For example, carbonic anhydrase produces acid in the stomach lining. Depending on its location, the role of the enzyme changes slightly. Ĭarbonic anhydrase helps maintain acid–base homeostasis, regulate pH, and fluid balance. The enzyme maintains acid-base balance and helps transport carbon dioxide. They are therefore classified as metalloenzymes. The active site of most carbonic anhydrases contains a zinc ion. 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. Human carbonic anhydrase II with bound zinc and carbon dioxide. ![]()
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