EFFECT OF METABOLITES ON CARBONIC-ANHYDRASE INDUCTION IN CHLORELLA-REGULARIS

When Chlorella regularis cells grown in air enriched with 3 % CO2 were transferred to ordinary air, an increase in carbonic anhydrase (CA) activity, located on the cell surface, was observed. The CA induction was strongly suppressed by the addition of glucose and acetate, and about 40 % by glycine. When 4 mM glucose was added, CA induction was suppressed for the first 2 h. But the suppression gradually diminished apparently in correlation with the consumption of glucose added externally. Glucose at 0.5 mM was enough to suppress CA induction completely, and 50 % suppression was obtained at almost 0.1 mM. Two millimolar L-methionine sulfoximine, 1 mM aminooxyacetate, and 1.8 mM alpha-hydroxypyridinemethane sulfonate (alpha-HPMS) suppressed CA induction completely, 20 % and 50 %, respectively. The suppression by alpha-HPMS was not removed by the simultaneous addition of 14.4 mM glyoxylate. These results suggest that CA induction under low CO2 is reversibly controlled by metabolites and also regulated by the operation of the glycolate pathway and the photorespiratory nitrogen cycle.