EXONUCLEASE ENZYME BY DHEERENDRA KUMAR

Описание: #NEET
#GATE BIOTECHNOLOGY
#CSIR NET
#Nucleases are enzymes that cut, shorten, or degrade nucleic acid molecules.
Nucleases degrade DNA molecules by breaking the phosphodiester bonds that link one nucleotide to the next in a DNA strand. There are two different kinds of nuclease
l Exonucleases remove nucleotides one at a time from the end of a DNA molecule.
lI Endonucleases are able to break internal phosphodiester bonds within a DNA molecule.
l Exonucleases-
Bal31 (purified from the bacterium Alteromonas espejiana) is an example of an exonuclease that removes nucleotides from both strands of a double-stranded molecule.
#In 1971, Lehman IR discovered exonuclease I in E. coli.
There are various type of exonuclease,I, II, III, IV, V, VI.
Each type of exonuclease has a specific type of function or requirement
Exonuclease I-
breaks apart single-stranded DNA in a 3' → 5' direction. It does not cleave DNA strands without  terminal 3'-OH groups because they are blocked by phosphoryl or acetyl groups.
#Exonuclease II is associated with DNA polymerase I, which contains a 5' exonuclease that clips off the RNA primer contained immediately upstream from the site of DNA synthesis in a 5' → 3' manner.
Exonuclease III has four catalytic activities:
3' to 5' exodeoxyribonuclease activity, which is specific for double-stranded DNA
RNase activity
3' phosphatase activity
AP endonuclease activity (later found to be called endonuclease II)