Topoisomerase function in DNA replication
Topoisomerase enzyme belong to a class of proteins that are catalysts. They have nuclease activity. Topoisomerase are enzymes that catalyze the over-winding which means leads to positive supercoiling of the DNA double helix or underwinding which means leads to negative supercoiling. Topoisomerase function in DNA replication are as follows:
Topoisomerase I in E.coli:
Relax or underwound negative supercoils only. It does not require cofactor.
Topoisomerase I in Eukaryotes
Relax or underwound positive and negative supercoils both. It does not require cofactor.
Topoisomerase 2 (Gyrase) in E.coli:
It requires ATP and increases negative supercoiling in both positive and negative supercoils.
Topoisomerase 2 in Eukaryotes:
It requires ATP AND Relax or underwound negative supercoils only.
How does DNA supercoiling arise?
DNA supercoiling arise by rotation of DNA induced by topoisomerase. Topoisomerase are enzymes that catalyze the over-winding which means leads to positive supercoiling of the DNA double helix or underwinding which means leads to negative supercoiling.
Positive supercoiling is over rotation and negative supercoiling is under rotation. Over rotation defines right-handed means twisted more tightly. Negative supercoiling is the left-handed which means removes knot by moving in negative direction.
Other functions of Topoisomerase
They are also known as polysaccharides and play a vital role in many physiological processes such as the metabolism of sugars and starch. Enzymes that belong to this class are used to break down different types of polysaccharides and starches including many kinds of polysaccharides derived from plant sources. Examples of the polysaccharides affected by enzymes in this class include: mucopolysaccharides, mucins, sericin, globulins, fibrins, mucilage, plasma proteins, low-density lipoproteins (LDL), high-density lipoproteins (HDL) and glycans. It is important to realize that these polysaccharides have different shapes depending on their origination and decomposition processes.
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