Carbonic anhydrase in carboxysome, molecular model. Computer illustration of a carbonic anhydrase molecule (pink-white, centre) with a water molecule (red-whit, left) and carbon dioxide molecules (top right, bottom left) inside a carboxysome (background). Carboxysomes are organelles found in the cells of photosynthetic bacteria and are primarily involved in the process of carbon fixation. They are composed of a polyhedral protein shell (green) filled with the enzyme Ribulose-1, 5-biphosphate carboxylase/oxygenase (RuBisCO, white-orange) and carbonic anhydrase (CA, fuchsia-pink). Carbonic anhydrases are enzymes that catalyse the rapid interconversion of carbon dioxide and water to bicarbonate and protons, a reversible reaction that occurs relatively slowly in the absence of a catalyst. RuBisCO is the predominant enzyme in carbon fixation - the process of converting inorganic carbon from forms such as carbon dioxide, to organic compounds by living |