In: Chemistry
Please post a detailed explaination:
Compare and contrast the actions of ribonuclease and restriction enzymes as to substrate choice and mechanism. Show how their strategies are similar, but also why they must use different strategies.
Action of ribonuclease -
Ribonuclease (commonly abbreviated
RNase) is a type of nuclease that catalyzes the
degradation of RNA into smaller components.
The RNA strand of DNA-RNA hybrids is cleaved by the enzyme RNase H,
an enzyme that exists in both the nucleus and cytoplasm of
eukaryotic cells. This catalytic cleavage can be exploited by
synthetic oligonucleotides to increase potency. “Gapmer”
oligonucleotides contain 2–5 chemically modified nucleotides (e.g.
LNA or 2′-MOE) on each terminus flanking a central 8-10 base “gap”
of DNA. The chemically modified oligonucleotides increase nuclease
resistance and increase affinity for target sequences, while the
DNA gap permits formation of a DNA-RNA hybrid that can be a good
substrate for RNase H.
Action of restriction enzyme - A
restriction enzyme or restriction
endonuclease is an enzyme that cuts DNA at or near
specific recognition nucleotide sequences known as restriction
sites. To cut DNA, all restriction enzymes make two incisions, once
through each sugar-phosphate backbone (i.e. each strand) of the DNA
double helix.
Restriction enzymes recognize a specific sequence of nucleotides
and produce a double-stranded cut in the DNA. The recognition
sequences can also be classified by the number of bases in its
recognition site, usually between 4 and 8 bases, and the amount of
bases in the sequence will determine how often the site will appear
by chance in any given genome.
Similar to restriction enzymes, which cleave highly specific sequences of double-stranded DNA, a variety of endoribonucleases that recognize and cleave specific sequences of single-stranded RNA have been recently classified.