| Carbonic anhydrase is widespread in nature, being found in animals, plants, and certain bacteria. In animals it plays an important role in respiration by facilitating transport of CO2 and is involved in the transfer and accumulation of H+ and HCO3-. In chloroplasts of plant cells the role of carbonic anhydrase may be related to photosynthetic fixation of CO2. Mammalian carbonic anhydrases are of several forms differing in enzymatic properties, amino acid sequences and inhibitor binding. In erythrocytes there is usually present both a high activity and a low activity form. The pH-rate profiles and pH-binding curves indicate that the same group with pKa of approximately seven is involved in both forms. All the isoenzymes have a molecular weight of approximately 30,000 and contain one zinc atom per molecule. Although Deutsch et al. (1972) report six carbonic anhydrases in horse red blood cells, most interest has been focused on high and low activity types. Bovine erythrocytes contain two electrophoretically separable forms designated A and B in order of mobility. Both have a high order of activity similar to the human variant ''C. Lindskog et al. (1971) devote a section of their review to polymorphism and nomenclature (pg. 595). The outstanding characteristic of carbonic anhydrase is its very high turnover number. Zinc may be replaced by cobalt. Shinar and Navon (1974) found that the cobalt-substituted enzyme is dependent upon the state of oxidation of the metal. Appleton and Sarkar (1974) indicate the activity is related to the ionization of a group close to the zinc. Appearance: Supplied as a dialyzed, lyophilized powder. Activity: 3000 W-A units/mg Unit Definition: The activity is determined by the time required (in seconds) for a saturated CO2 solution to lower the pH of 0.02M TrisHCl buffer form 8.3 to 6.3 at 0C. Optimum pH: 7.0-7.5 (Demir et al. 2000, and Tasgin et al. 2009) Activators: HPO42-(Rowlett et al. 1991), SO32-(Rowlett et al. 1991) Storage and Stability: Lyophilized powder may be stored at 4C. Stable for 6 months after receipt at 4C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer. Certificate of Origin: All products from animal sources are produced from starting material of USDA-approved origin, collected in USDA or equivalent approved facilities, inspected to be free of disease and suitable for exportation. |
