On the stability of sulfhydryl-containing carbonic anhydrases

1. 1. Carbonic anhydrase in lysates of chicken red blood cells experienced only a small loss (5%) in activity for periods of up to a week when dithiothreitol was present; without sulfhydryl protection activity was reduced by 90%. 2. 2. The presence of cell particulate material in the lysate contributed in a major way to the enzyme stability; when particulate material was removed an activity loss of about 70% occurred over a week's time even though dithiothreitol was present. 3. 3. The widespread phenomenon of a requirement for sulfhydryl protection by submammalian carbonic anhydrases is discussed.