Exam 3 Biochem-Lecture 35

Deoxyribonucleotides are formed by
 the reduction of ribonucleoside diphosphates.

 

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

 ribonucleotides

 

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????
UMP

 

nPyrimidine nucleotides are degraded to ….?

b-amino acids

 

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

interconvertible

For example – UMP → UDP → UTP

 

Specific nucleoside (X) monophosphate kinases make

nucleoside diphosphates

 

XMP + ATP   –>XDP + ADP

 

 

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

dinucleosides and trinucleosides
Nucleotide coenzymes are

 

nNAD
nFAD
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
5-phosphoribosyl-1-pyrophosphate
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
purine
AZT is a …… analog
pyrimidine

 

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