MBIO 2370 Lecture Notes - Lecture 17: Dihydrofolate Reductase, Thioredoxin Reductase, Thymidine Monophosphate
5 Apr 2017
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Document Summary
As with purines each atom of the pyrimidine ring has a unique origin, but here there are only 2 precursors (carbamoyl phosphate and aspartate) This suggests a much simpler biosynthetic pathway. The major difference between the pyrimidine and purine pathways is that the pyrimidine ring is built independently and then added to the ribose by a phosphoribosyl transferase late in the synthesis. Unlike purine nucleotides, pyrimidine rings are made independently of the sugar base and then added to ribosep (using phosphoribose pyrophosphate, prpp) to create the nucleotide. Glutamine + co2 + 2 atp into carbamoyl phosphate. Orotidine monophosphate (omp) into uridine monophosphate (ump) Addition of phosphate groups are through kinases. Removal of phosphate groups are through pyrophosphatases. Add sulphur to cytosine than do a deamination. If cytosine if methylated, cannot add sulphur because there is no double bond. Unmethylated cytosine will become uracil when deaminated. Nucleotides are synthesized in the ribose form, used in rna.
