Carbonic Anhydrase of Chlamydomonas: Purification and Studies on its Induction Using Antiserum against Chlamydomonas Carbonic Anhydrase

Carbonic anhydrase (EC 4.2.1.1; CA) was purified by affinity chromatography from cells of the unicellular green alga Chlamydomonas reinhardtii which had been grown photoautotrophically in ordinary air. Antiserum raised in rabbit against this purified CA crossreacted with Chlamydomonas CA but not with spinach leaf CA nor bovine erythrocyte CA. When the CO2 concentration provided to the algal cells was decreased from 4% to the ordinary air level (0.04%), CA activity and the content of CA protein determined by the immunodiffusion test showed parallel increases. In contrast, when the CO2 concentration was raised from air level to 4% CO2 CA activity and its content expressed on the basis of culture volume remained rather constant. These results indicate that synthesis of the CA protein is induced when the CO2 concentration is lowered from 4 to 0.04% during algal growth. On the other hand, the synthesis of CA stops when CO2 concentration is raised from air level to 4%.