Without proper intake of metals such as zinc in a persons diet, the activity of the enzyme would be inhibited. In other metalloenzymes the metal is built into the structure of the enzyme molecule. The metal ion can not be removed with out destroying the structure of the enzyme. Metals are usually found in the active site of the enzyme. Metal's larger size relative to protons is compensated for by their ability to react with more than one ligand.
Metals typically react with two, four, or six ligands.
A ligand is whatever molecule the metal interacts with. If a metal is bound with two ligands it will form a linear complex. If the metal reacts with four ligands the metal will be set in the center of a square that is planer or it will form a tetrahedral structure, and when six ligands react, the metal sits in the center of an octahedron. The fact that metals bind to several ligands is important in that metals play a role in bringing remote parts of the amino acid sequence together and help establish an active conformation of the enzyme. The zinc atom serves as a metal ion catalyst and promotes hydrolysis.