One might legitimately suspect that enzymatic activity
narallels the bindine streneth between aoocarbonic anhvdrase
and various cations. Do zrnc(11) and cobalt(11) hind particularly
strongly to apocarbonic anhydrase compared with other
metal ions? Lindskog and Nyman (9) have measured the
hindin:: cunstants under limitrd t.trnditiwls tnr .everal mernl
i.,n-humnn wrl~onir iltthvdr;r+e coml,lrw.;. .%I pH 5.5. rhr
following stability constants, expressed as log K values, were
reported: Hg(I1)CA (21.5); Cu(1I)CA (11.6); Zn(1I)CA (10.5);
Ni(lI)CA (9.5); Cd(I1)CA (9.2); Co(I1)CA (7.2); and Mn(II)CA
(3.8). Since the zinc(I1) and cobalt(I1) derivatives are the only
active complexes and they are interspersed among other
species of both greater and lesser stahility, it is doubtful that
enzymatic activity correlates in any direct way with the
strength of binding between apoCA and the metal ions under
investigation.