The effect of zinc on the activity and fluorescence of carbonic anhydrase holoenzymes.
The addition of Zn2+ to human carbonic anhydrase B holoenzyme was shown to enhance the protein fluorescence, and this enhancement was correlated with the inhibition of the p-nitrophenyl acetate esterase activity. The affinity for the inhibitory Zn2+ was increased when the ionic inhibitors, acetate or chloride, were added, suggesting that the inhibitory Zn2+-binding site is within the region of the protein that undergoes an anion-induced conformational change. A similar fluorescence enhancement was observed when Zn2+ was added to human carbonic anhydrase C and to bovine carbonic anhydrase, demonstrating that the binding site is not a thiol group. Circular-dichroism studies showed that the C isoenzyme but not the B isoenzyme underwent a major conformational change in the presence of Zn2+. A mechanism for the Zn2+-induced fluorescence enhancement was suggested on the basis of studies with simple compounds.
D000085:Acetates; D001665:Binding Sites; D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides; D002942:Circular Dichroism; D004950:Esterases / Q000037:antagonists & inhibitors; D006801:Humans; D007527:Isoenzymes; D007700:Kinetics; D009596:Nitrophenols; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D015032:Zinc
D000085:Acetates; D002257:Carbonic Anhydrase Inhibitors; D002712:Chlorides; D007527:Isoenzymes; D009596:Nitrophenols; D004950:Esterases; D015032:Zinc