Question

3. One third of all enzymes are metalloproteins. Describe two examples where metals function in enzyme catalysis. For each state the reason the metal is employed. (15 points)
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Answer 1

3. Metalloprotein is a general name for a protein with a metal ion cofactor or a metal ion in the non protein part to increase the enzymatic activity.It is a fact that about on third of all the proteins require metals to carry out their functions.The functions of metalloproteins include transport and storage and enzymatic activity.Metals in the human body are bound to proteins.

Metalloenzymes are the one in which a metal ion is bound to the labile coordination site.the shape of the active site is very important . some examples of the metalloenzymes are carbonic anhydrase, cobalamin, nitrogenase, chlorophyll, hydrogenase, ribozyme, carboxy peptidase etc,..

CARBONIC ANHYDRASE

The formation of carbonic acid is a very slow reaction in the absence of a catalyst while it is instantaneous with carbonic anhydrase. It consists of ZINC ion coordinated by three imidazole nitrogen atoms from three histidine units.the fourth site is occupied by water molecule. the carbonic anhydrase thus have zinc with tetracoordinated system almost tetrahedral, catalysing the dissociation of carbonic acid into bicarbonate ion and hydrogen ion at equilibrium.

CHLOROPHYLL

Chlorophyll plays an important role in photosynthesis and it contains magnesium enclosed in chlorin ring.