[Activation of carbonic anhydrase from rat gastric tissue as a result of phosphorylation by 3',5'-AMP-dependent protein kinase].

Two isoenzymes of carbonic anhydrase, one with high activity and the other with low activity, were isolated from rat gastric tissue. It was found that both isoenzymes were phosphorylated in vitro by protein kinase isolated from gastric mucosa and that this process was stimulated by 3',5'-AMP. The phosphorylation of highly active carbonic anhydrase isoenzyme is shown to result in the increase of its activity. The phosphorylation of low active carbonic anhydrase isoenzyme did not affect its activity or decreased it slightly. The results obtained suggest that the activation of carbonic anhydrase in vivo by gastrin (pentagastrin), histamine and 3',5'-AMP is due to the phosphorylation of highly active isoenzyme by 3',5-AMP-dependent protein kinase. It seems possible that in this process histamine and 3',5'-AMP act as sequential mediators of pentagastrin effect.