Carbonic anhydrase experimental methods

The dimeric nature of alkaline phosphatase makes it a more complicated system than carbonic anhydrase or carboxypeptidase. The enzyme contains several metal-binding sites. The stoichiometry of zinc binding is not completely settled. There are at least two strongly bound metal ions (109, 111, 114), but the presence of four specific sites has been claimed (115, 116). At alkaline pH, the enzyme tends to bind even more zinc rather strongly, but probably to sites unrelated to catalytic function (109). A critical evaluation of this aspect falls outside the scope of this review, but it appears that some of the apparent discrepancies are due to different experimental methods in measuring metal binding. 

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