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An enzyme that catalyzes the splitting of nucleic acids to nucleotides, nucleosides, or the components of the latter.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a phosphodiesterase enzyme that splits nucleic acids into mononucleotides and oligonucleotides.

Nucleases are widely distributed in the cells of microorganisms, plants, and animals. These enzymes are especially abundant in pancreatic juice and in the saliva of mammals and man. A distinction is made between 3′ and 5′ nucleases, depending on whether the enzyme splits the phosphodiester bonds of the nucleic acid to form nucleotides that contain phosphoric acid residues on the 3’- or 5’-carbon of the carbohydrate fragment. The terminal mononucleotides are separated by exonucleases; nucleases that split bonds within the polynucleotide chain are called endonucleases. Ribonucleases and deoxyribonucleases are distinguished according to whether they split ribonucleic or deoxyribonucleic acids. Nonspecific nucleases are able to split chains of both types of acids.

Nucleases are proteins—usually basic—with a comparatively low molecular weight; for example, the pancreatic ribonuclease molecule consists of 124 amino-acid residues. The biological function of nucleases is to digest and split nucleic acids that are foreign to the organism, for example, nucleic acids of invasive viruses. This is the rationale for using nucleases to treat certain viral diseases. Nucleases participate in the repair of deoxyribonucleic acid (DNA) by eliminating the fragmented portions of the DNA molecule from the polynucleotide chain. Nucleases also appear to play a major role in regulating the synthesis and decomposition of nucleic acids in cells. A nuclease enzyme can be used in laboratories to free preparations from a specific nucleic acid, to determine the structure of nucleic acids, and to study the mechanism of nucleic acid decomposition and synthesis.


Shapot, V. S. Nukleazy. Moscow, 1968.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The structure of the bacterial Thermus aquaticus Polymerase 1 revealed a relatively conserved fold for the 5'-3' exonuclease domain that shares homology with the flap endonuclease proteins (Figure 2(c)).
Tainer, "Structure of the DNA repair and replication endonuclease and exonuclease FEN-1: coupling DNA and PCNA binding to FEN-1 activity," Cell, vol.
Sayers, "Unusually wide co-factor tolerance in a metalloenzyme; divalent metal ions modulate edno-exonuclease activity in T5 exonuclease," Nucleic Acids Research, vol.
The 3' phosphorylated primers were used for the digestion of dsDNA by lambda exonuclease in order to get ssDNA.
To optimize lambda exonuclease reaction, 5 pg of the purified dsDNA was incubated with 5 U lambda exonuclease in a total reaction volume of 30 [micro]l in a reaction buffer at 37[degrees]C.
Results of dsDNA digestion by lambda exonuclease at different incubation times were analyzed on the 10% denaturing-urea PAGE (Figure 6).
The associated 5'-3' exonuclease activity of the DNA polymerase makes possible the synthesis of extension products derived from upstream primers even in the presence of downstream primers.
For example, degradation of downstream primer extension products might not be complete at each cycle because of premature termination of primer extension or <100% efficiency of the polymerase 5'-3' exonuclease activity.