Nucleotide Metabolism

(Voet & Voet Chapter 26)

Anabolism :

Nucleotides :
1). PRPP, synthesized from ATP and R5P, is the precursor of the purine biosynthesis intermediate IMP. IMP is converted to AMP and GMP, than phosphorylated to ATP and GTP.

2). How is the purine nucleotide biosynthesis regulated? Which enzyme is activated by PRPP?

3). How are the purines and pyrimidines salvaged in cells?

4). Why does the patient with Lesch-Nyhan Syndrom produce excessive amount of uric acid?

5). The free base, orotate, is synthesized by enzymes, including carbamoyl phosphate synthetase II, in cytosol, and than is converted to UMP with PRPP.

6). How is the pyrimidine nucleotide biosynthesis regulated?

Deoxynucleotides :

7). What is the difference between multifunctional enzyme and multienzyme complex? What is their biological significance?

8). Deoxynucleotides are produced by converting NDP by ribonucleotide reductase. How is this enzyme regulated?

9). Thymine : dTMP is synthesized from dUMP and N5, N10- methylene-THF by thymidylate synthase (inhibitor: FdUMP, 5-Fluorouracil). DHF is regenerated by DHFR (inhibitor: methotrexate, aminopterin) and serine hydoxymethyl transferase.

10). How is the proper intracellular ratio of dNTPs controlled? Why does it need to be controlled?

Catabolism : 11). Purine nucleotides are converted to uric acid via xanthine. Pyrimidines are catabolized in animal cells to amino acids. Nucleotide Coenzymes : 12). NAD and NADP  are synthesized from Trp, nicotinate, and nicotinamide. FMN and FAD are synthesized from riboflavin & ATP. Pantothenate is the precursor of CoA. Practice Problem : Question 10 and 13, Chapter 26 (Veot & Veot p.828).

Last modified on 1999.3.28 by K.-J. Hsiao (s)                                        [ ]