Purification and localization of human carbonic anhydrase. III. Typing of skeletal muscle fibers in paraffin embedded sections.

Three different isoenzymes of human carbonic anhydrase are now well characterized. Carbonic anhydrase I and II have been known for several years and are located in high amounts in red blood cells as well as in many other tissues. Carbonic anhydrase III, a protein showing CO2 hydratase and p-nitrophenylphosphatase activity was isolated from skeletal muscle some years ago. Earlier observations based on enzyme activity and radioimmunoassay studies have suggested that this protein is present in greater quantities in red skeletal muscles than in white ones. We have purified CA III from human soleus muscle and using obtained monospecific polyclonal antibody localized this protein in the same muscle fibers which show acid resistant ATPase activity. Using this protein as a marker for type I muscle fibers, fiber classification into type I and II could now be done also from paraffin embedded sections.