Nuclease

Nucleases are a group of enzymes, whose main function is to partial or complete degradation of nucleic acids. We also talk about partial or complete digestion of a substrate.

Classification criteria

There are various features of nucleases, which sometimes serve as criteria for their classification:

  • Type of priority digested nucleic acid, RNA ( ribonucleases, RNases short ), DNA ( deoxyribonucleases, short DNases ), RNA and DNA ( no specific denomination ).
  • Type of the secondary structure of the substrate: single or double stranded, single stranded or double strands.
  • Type of digestion: Removal from the end ( exonucleases ), internal interface ( endonucleases ), reduction of external and internal cuts.
  • Of attack in the sugar - phosphate backbone: between phosphate and 5' -site of the ( deoxy ) ribose, phosphate- 3' -site of the ( deoxy ) ribose.
  • Role of a specific base sequence: a sequence-specific, sequence- nonspecific.
  • Origin: naturally occurring nucleases, nucleases recombinant ( genetically engineered ).

Mostly nucleases are named according to their origin. For this purpose the naturally occurring nucleases are often named after the type of organism in which it arises and numbered in the order of their isolation and characterization. So EcoRI restriction endonuclease is the I. of the bacterial strain " Escherichia coli R".

Examples

The classification according to different criteria is not intended to be exhaustive, especially as there are for a finer divisions and on the other many nucleases have no clearly identifiable characteristics. A finer classification is for instance the exonucleases, which is oriented to the direction of the digestion and for endonucleases has no relevance ( 5'-3 ' and 3'-5' exonucleases ). The sequence-specific double-stranded restriction endonucleases (also called restriction enzymes) are in turn divided into types I to III according to the relationship between binding and interfaces.

System

After the enzyme classification system of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology ( IUBMB - NC ), the vast majority of nucleases hydrolases ( EC 3 ), acting on ester bonds ( EC 3.1 ). The esterases, which digest nucleic acids are summarized there in groups EC 3.1.11 to 3.1.31 EC.

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