Question

7. A researcher has just made the observation that a newly identified protein (currently named protein A) binds with nearly equivalent affinity to Ca> and Fe?". Moreover, bound metal appears to be required for catalytic function. However, the enzyme-catalyzed reaction appears to be much faster in the presence of cao". Please briefs propose an explanation for this observation. Why does compromete increased reaction rates relative to F-2 (10 Points) aute na How he p kad

Answer 1

Enzyme can be purely proteinaceous in nature or there may exist a non-protein part as well. The protein part is called the APOENZYME and the non-protein part is called the COFACTOR.

The cofactors are bound to the enzyme to make the enzyme catalytically active.There are three types of cofactors-

Prosthetic groups are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme.

Co-enzymes are also organic compounds but their association with the apoenzyme is only transient, usually occurring during the course of catalysis. Furthermore, co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin.

A number of enzymes require metal ions for their activity which form coordination bonds with side chains at the active site and at the same time form one or more cordination bonds with the substrate, e.g., zinc is a cofactor for the proteolytic enzyme carboxypeptidase. Catalytic activity is lost when the co-factor is removed from the enzyme which testifies that they play a crucial role in the catalytic activity of the enzyme.

Which metal is useful for what reaction is all based on coordinate geometry.There may be two reasons for Calcium to be more effective than Iron:

1) Fe⁺² can easily oxidise to Fe⁺³ . The requirement for the substrate molecule to get attached to the enzyme must be of +2 charge. And this could not be facilitated by Fe⁺³ and hence here Ca⁺² comes into work and thus more productive than iron ion.

2)In some cases like EDTA, Ca⁺² ions restores the visible spectrum . EDTA forms chelate and abolishes the enzymatic activity. And this can be only restored by Ca⁺² ions. So its just not sufficient to carry the same charge as Ca to function in a same way.