Regulation of prokaryotic adenylyl cyclases by CO2
Résumé
The Slr1991 adenylyl cyclase of the model prokaroyte Synechocystis PCC 6803 was stimulated two-fold at 20 mM total inorganic carbon at pH 7.5 through an increase in k cat}. A dose response demonstrated an E.C. 50} of 52.7 mM total inorganic carbon at pH 6.5. Slr1991 was activated by CO 2} but not HCO 3} -}. CO 2} regulation of adenylyl cyclase was conserved in the CyaB1 adenylyl cyclase of Anabaena PCC 7120. These adenylyl cyclases represent the only identified signalling enzymes directly activated by CO 2}. The findings prompt an urgent reassessment of the activating carbon species for proposed HCO 3} -} activated adenylyl cyclases.
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