Question

Biochemistry help

Cordycepin, or 3-deoxyadenosine, is a derivative of the nucleoside adenosine, differing from the latter by the absence of oxygen in the y position of its ribose part. It was initially extracted from fungi of genus Cordyceps. Cordycepin inhibits poly(A) synthesis at low concentrations and RNA synthesis at higher concentrations. Please draw the structure of cordycepin. What is the basis of inhibition by cordycepin? Why poly(A) synthesis is more sensitive to cordycepin? Does codycepin need to be modified to exert its effect? Explain

Answer 1

Cordycepin (3' - deoxyadenosine) is a derivative of the nucleotide adenosine and acts like a nucleoside analogue. It is extracted from the fungus Cordyceps militaris. It has a anticancer, antioxidant and antiinflammatory activities.Cordycepin interferes with the various biochemical and molecular processes that includes purine biosynthesis, DNA/RNA synthesis and mTOR (mammalinan target of rapamycin) signaling transduction.

Answer b:

As cordycepin lacks 3' hydroxyl group (is the only difference from adenosine), it will not involve in 3' $\rightarrow$ 5' bond formation.

Answer c:

Poly (A) synthesis is more sensitive to cordycepin because poly (A) tail is a long stretch of adenosine nucleotides, the cordycepin molecule that can incorporate is higher than RNA.

Answer d:

Cordycepin need to be modified to cordycepin 5'-triphosphate to exert its effect. cordycepin 5'-triphosphate specifically inhibits the polyadenylating enzyme in the nucleus and the formation of poly (A) at the 3' end of the mRNA is blocked by cordycepin 5'-triphosphate.  

References:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3909570/

https://www.ncbi.nlm.nih.gov/books/NBK22543/

http://nar.oxfordjournals.org/content/21/12/2917.short