USMLE forum
 
USMLE Forum
Step 1
Step 2 CK
Step 2 CS
Matching & Residency
Step 3
Classifieds
 
Archives
 
 
  <<   < *  Step 1   *  >   >>  

* My BASIC UNDERSTANDING :) of Pyrimidine & Purine
 #677126  
  zen786 - 05/15/12 14:29
 
  BIG PICTURE :

dietary product consumed : --> Glycine [source = turkey, chicken, etc]
dietary product consumed : --> glutamine [ source = milk, yogurt, cheese, beef, etc]
dietary product consumed : --> aspartate [ source = fish, nuts, vegetables, etc]

after protein metabolism amino acids are absorbed for use. [the ones listed above and many other] but we shall discuss the use of the amino acids listed above.

De Novo Pyrimidine & Purine synthesis: Well we start of with Ribose 5 - phosphate [R5P]
... where does ribose 5 phosphate come from? well its from HMP SHUNT PATHWAY.. please read HMP SHUNT for further understanding and development of R5P.

R5P -> will eventually become PrPP via addition of salvage nucleosides* note i did not say nucleotides***
so R5P + Adenine + respective enzyme = AMP
etc etc for further http://en.wikipedia.org/wiki/Phosphoribosyl_pyrophosphate check chart***

now that we have R5P converted to PrPP that is still not enough for Pyrimidine synthesis yet it is enough for Purine synthesis to begin solo just via PrPP and respective enzymes....


Pyrimidine synthesis also requires OROTIC ACID. which requires Precursors known as Carbon dioxide, ATP [ source of ATP = mutliple] , Glutamine. these are the precursors for OROTIC ACID.... ofcourse for pyrimidine we also require aspartate but that will come after....


now that we have Orotic acid made + PrPP we can continue our cycle for pyrimidine synthesis and make UMP* uridine [other sources = tomatoes, sugarcane, beer, etc]

so continuation of pyrimidine synthesis: after we have UMP we need it to become UDP... after it becomes UDP it needs to become deoxy from oxy* so ribonucleotide reductase comes over and takes away a electron as this is a reduction enzyme ... a gaining enzyme ... making it dUDP and also from UDP you get CTP which eventually becomes cytidine.

now dUDP will not function in dna so after become dUMP + thymidylate synthase + Dihydrofolate reductase to make THF + SAM you will now have dTMP* allowing to make thymidine

here you have THYMIDINE & CYTIDINE

now back upto PrPP you will require all 3 amino acids listed above [ glycine, glutamine, aspartate + THF and + major enzyme = glutamine PrPP amidotransferase = ratelimiting to make IMP* [inosine monophosphate other source = flavor enchancer] which then plus IMP dehydrogenase + either aspartate or glutamine will give you either AMP or GMP


by this u have GUANOSINE & ADENOSINE


just remember Thymidine = Uracil in RNA :)

hope this isn't too much this is the story i just made to remember and help me recall :) goodluck everyone hope i didn't confuse anyone !!! if so please ask away & also if any errors please let me know :)
 
Report Abuse

 
 

* Re:My BASIC UNDERSTANDING :) of Pyrimidine & Purin
#2694688
  zen786 - 07/12/12 15:55
 
  just thought i'd bump this because i was studying this page of biochemistry in my first aid for all those that might of missed it on the original date of post... if it benefits bravo if not im sorry for further confusion lol :) cheers  
Report Abuse

          Page 1 of 1          

[<<First]   [<Prev]  ... Message ...  [Next >]   [Last >>]

 
Logon to post a new Message/Reply
 
 
 
 

 

 

Google
  Web USMLEforum.com
 

Step 1 Step 2 CK Step 2 CS Matching & Residency Step 3 Classifieds
LoginUSMLE LinksHome