Deoxyribonucleotide synthesis

Question 1

NDP - > dNDP

Answer 1

NADPH -> NADP+

enzyme: RIBONUCLEOTIDE REDUCTASE

Question 2

Regulation of Ribonucleotide reductase

Answer 2

Induction:
-S-phase enzyme-active in dividing cells
-R1: catalytic subunit, constitutive expression
-R2: regulatory subunit, induced in S-phase
Allosteric:
-dATP: complete inhibition
-dGTP: +ADP -GDP,UDP,CDP
-dTTP: +GDP -UDP,CDP

Question 3

Thymidylate synthase reaction

Answer 3

dUMP + 5N10N methylene THF -> dTMP + H2F
enzyme: TMP-S

inhibited by: 5F-dUMP

Question 4

Deoxycytidine kinase dCK

Answer 4

dCit + ATP -> dCMP + ADP

• lymphoid specific
• broad substrate specificity
• substrates: dAde, dGua, dCit
• analogues: antileucemic agents

Question 5

Thymidine kinase dTK

Answer 5

thymidine + ATP -> dTMP + ADP

• S phase dependent
• human: narrow specificity
• herpes: wide specificity- selective inhibition