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 zeta-class carbonic anhydrase (CAs, EC 4.2.1.1) from the diatom Thalassiosira weissflogii (TweCA zeta) 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. CdTweCA zeta was completely insensitive to activation, whereas all these compounds were effective activators of the zinc-containing enzyme ZnTweCA zeta with activation constants ranging between 92 nM and 37.9 mu M. The most effective ZnTweCA zeta activators were L-adrenaline, 1-(2-aminoethyl)-piperazine and 4-(2-aminoethyl)-morpholine, with K(A)s in the range of 92-150 nM. L-His, L- and D-Tyr and some pyridyl-alkylamines, had K(A)s in the range of 0.62-0.98 mu M, whereas L-/D-DOPA, D-Trp, histamine, serotonin and L-Asn were the next most efficient activators, with K-As in the range of 1.27-3.19 mu M. The least effective activators were L-Phe (K-A of 15.4 mu M) and L-Asp (K-A of 37.9 mu M). This in vitro study may be useful for a more complete understanding of the activation processes of various CA enzyme families, of which the zeta-class was scarcely investigated.