Question

Enzymes with heme as prosthetic group are
a) Catalase
b) Carboxypeptidase
c) Succinic dehydrogenase
d) peroxidase

A) a and d
B) a only
C) a and b
D) b and c
E) c and a

Answer 1

Hint: Enzymes are proteinaceous compounds which act as a biological catalyst and help in speeding up the reaction speed. They are not destroyed during the course of the reaction.

Complete answer:
Prosthetic groups are bound tightly to protein and may even be attached to a covalent bond as opposed to cosubstrates which are loosely bound. In enzymes prosthetic groups are often involved in the active site playing an important role in the function of the enzymes.

Inorganic prosthetic groups however are usually transition metal ions such as iron. The heme group is hemoglobin is the prosthetic group located in the porphyrin, which is the tremor of cyclic carbon group. It contains an organic component called protoporphyrin made up of four pyrrole rings and an iron atom in the ferrous state.

Blood and muscles is attributed to the heme group. Heme is a prosthetic group which contains iron and it is present in cytochrome, catalase, peroxidase, myoglobin and haemoglobin.

In catalase, the function of heme is not very defined and its main function is decomposition of hydrogen peroxide into water and oxygen. On the other hand, peroxidase is a group of enzymes which can catalyse the substrate oxidation by an organic or hydrogen peroxide. Most of the peroxidases contain ferric heme proteins.

Therefore, the correct answer is option (A) i.e, a and d.


Note: The function of catalase and peroxidase is as follows,
i) Catalase - It is found in peroxisomes in mammalian cells and it prevents collecting and also give protection of cellular organelles and tissues from damage that can be caused by peroxide
ii) Peroxidase - It is found in wide range of organisms and its major function is to break down hydrogen peroxide which is produced as a byproduct of using oxygen during respiration