The zinc – but not cadmium – containing ζ-carbonic from the diatom Thalassiosira weissflogii is potently activated by amines and amino acids

The activation of the ζ-class carbonic anhydrase (CAs, EC 4.2.1.1) from the diatom Thalassiosira weissflogii (TweCAζ) incorporating both Zn(II) and Cd(II) at the active site, was investigated for the first time, using a panel of natural and non-natural amino acids and amines. CdTweCAζ was completely insensitive to activation, whereas all these compounds were effective activators of the zinc-containing enzyme ZnTweCAζ, with activation constants ranging between 92 nM and 37.9 µM. The most effective ZnTweCAζ activators were l-adrenaline, 1-(2-aminoethyl)-piperazine and 4-(2-aminoethyl)-morpholine, with KAs in the range of 92-150 nM. l-His, l- and d-Tyr and some pyridyl-alkylamines, had KAs in the range of 0.62-0.98 µM, whereas l-/d-DOPA, d-Trp, histamine, serotonin and l-Asn were the next most efficient activators, with KAs in the range of 1.27-3.19 µM. The least effective activators were l-Phe (KA of 15.4 µM) and l-Asp (KA of 37.9 µM). This in vitro study may be useful for a more complete understanding of the activation processes of various CA enzyme families, of which the ζ-class was scarcely investigated.