Interaction of lead ions with bovine carbonic anhydrase

The interaction of lead (Pb2+) ions with apocarbonic anhydrase is studied by u.v. difference spectroscopy. The Pb2+results are compared with those of Zn2+interacting with apocarbonic anhydrase. The results of both metals interacting with apoenzyme are related to the difference spectra of Pb2+and Zn2+with Trp and Tyr model compounds. The interaction of Pb2+with apocarbonic anhydrase containing an acetylated tyrosine residue is examined. Evidence is presented that Pb2+is located in the active site cavity of apocarbonic anhydrase, but displaced from the zinc His ligands, interacting with Tyr 7. An attempt is made to rationalize the metal‐chromophore micro‐environment based on analysis of the 270–295 nm u.v. region of the difference spectra.