Question

1. What are the biological functions of lectins?

2. What are the biological functions of peroxidase?

(Answer Must be brief)

Answer 1

Lectins :

Lectins are proteins that recognize and bind specific carbohydrates found on the surfaces of cells. They play a role in interactions and communication between cells typically for recognition.

They can bind to soluble carbohydrates or carbohydrate functional groups that are a part of a gylcoprotein or glycolipid.

Lectins typically bind these carbohydrates with certain animal cells and sometimes results in glycoconjugate precipitation.

In animals, lectins regulate the cell adhesion to glycoprotein synthesis, control protein levels in blood, and bind soluble extracellular and intracellular glycoproteins. Also, in the immune system, lectins recognize carbohydrates found specifically on pathogens, or those that are not recognizable on host cells. Clinically, purified lectins can be used to identify glycolipids and glycoproteins on an individual's red blood cells for blood typing.

Peroxidase :

The peroxidases are enzymes whose primary function is to oxidize hydrogen donors at the expense of peroxides. They are highly specific for hydrogen peroxide, but they accept a wide range of hydrogen donors, including polyphenols.

Peroxidase is an enzyme found in a wide variety of organisms, from plants to humans to bacteria.

Its function is to break down hydrogen peroxide (H₂O₂), which is one of the toxins produced as a byproduct of using oxygen for respiration.

The peroxidase reaction is as follows:

2 H₂O₂ + peroxidase ---> 2 H₂O + O₂ + peroxidase

Water and oxygen are much less toxic than H₂O₂, and thus don't damage the interior of the cell.

Peroxidases are a large family of enzymes that typically catalyze a reaction of the form:

ROOR' + 2e^-  + 2H⁺ -------Peroxidase---->> ROH + R'OH

For many of these enzymes the optimal substrate is hydrogen peroxide, but others are more active with organic hydroperoxides such as lipid peroxides. Peroxidases can contain a heme cofactor in their active sites, or alternately redox active cysteine or selenocysteine residues.