Exam 3 Biochem-Lecture 35

Deoxyribonucleotides are formed by
 the reduction of ribonucleoside diphosphates.


All deoxyribonucleotides are synthesized from ……….. by the enzyme ribonucleotide reductase.



nAll deoxyribonucleotides are synthesized from ribonucleotides by the enzyme …….

ribonucleotide reductase. (highly regulated)


                   Deoxthymidylate (dTMP) is

formed by

methylation of deoxyuridine 5’-mono Phosphate (dUMP)

what is the precursor for all the pyrimidine nucleotides????


nPyrimidine nucleotides are degraded to ….?

b-amino acids


Nucleotide mono-, di-, and triphosphates are …….


For example – UMP → UDP → UTP


Specific nucleoside (X) monophosphate kinases make

nucleoside diphosphates





• A nucleoside diphosphate kinase, with broad substrate specificity,interconverts………… (this enzyme uses both ribo and deoxynucleosides as substrates)

dinucleosides and trinucleosides
Nucleotide coenzymes are


nCoenzyme A (CoA)


NAD means

nicotinamide adenine dinucleotide


FAD means

Flavin Adenine Dinucleotide


nPRPP is the KEY molecule in


¨ de novo synthesis of purine and pyrimidine nucleotides
¨salvage of purine and pyrimidine bases
¨ and synthesis of NAD+.

PRPP means
dUMP can be converted to dTMP using this enzyme:

thymidylate synthase

thymidylate synthase
an enzyme targeted by anticancer drugs such as 5-flurouracil


nThe regeneration of THF from DHF produced in the thymidylate synthase reaction requires

dihydrofolate reductase
dihydrofolate reductase
an enzyme targeted by the drug, methotrexate.
Methotrexate is
Folic acid antagonist
Acyclovir is analog
AZT is a …… analog


nAcyclovir a purine analog, and AZT a pyrimidine analog are used in the treatment of

HSV and HIV infections.
Acyclovir, a purine analog, and AZT a pyrimidine analog are
antiviral agents
6-Mercaptopurine  is
purine analog
5-Fluorouracil is
pyrimidine analog
Cystonesine arbinoside is
pyrimidine analog