Lecture 21 - Nucleotide Metabolism

Question 1

The committed step of purine synthesis is _____.

Answer 1

PRPP to phsophoribosylamine (activated by the addition of C1 amine group)

Question 2

Closes the nitrogenous base in purine synthesis

Answer 2

tetrahydrofolate (specifically, N5-formyl THF)

Question 3

Reduces NDPs to dNDPs

Answer 3

ribonuclease reductase

Question 4

Inosinate is the intermediate in ___ and ___ production.

Answer 4

dATP and dGTP production

Question 5

Between __ and ___, the N-base rings are built in purine synthesis.

Answer 5

phosphoribosylamine; inosinate

Question 6

Closes the purine ring structure

Answer 6

N10-formyl THF

Question 7

Feedback inhibition of purine synthesis:

PRPP and PR-amine is inhibited by _____

Answer 7

IMP/GMP/AMP

Question 8

Step 1 of de novo purine synthesis occurs when ______ catabolizes ribose-5-phosphate to phosphoribosyl pyrophosphate

Answer 8

PRPP synthase

Question 9

Why is purine salvage an important biochemical process?

Answer 9

Pyrimidine triphosphates are important energy carriers (ATP; GTP), so they are salvaged to “run” other processes.

Question 10

Purine salvage involves the loss of ____ from ribose to attach the nitrogenous base.

Answer 10

C1 Pi (the inorganic phosphate from Carbon 1)

Question 11

Catalyst for AMP salvage

Answer 11

adenine phosphoribosyl-transferase (APRT)

Question 12

Catalyst for guanine salvage

Answer 12

Hypoxanthine-guanine phosphoribosyl-transferas (HGPRT)

Question 13

Pyrimidines are salvaged by ______.

Answer 13

Phorphorylases

Question 14

Phosphoribosyl-5-pyrophosphate (PRPP) is important as it is critical in the production of \_\_\_\_\_\_\_  \_\_\_\_\_\_.
A. ATP molecules
B. GTP molecules
C. FAD molecules
D. Purine nucleotides

Answer 14

D. purine nucleotides (A & G)

Question 15

GTP and ATP production use what for energy?

Answer 15

ATP for GTP production

GTP for ATP production

Question 16

IMP production is inhibited by _____.

Answer 16

AMP/GMP

Question 17

GMP production is stimulated by _____.

Answer 17

ATP (ATP needs more GMP to bind to)

Question 18

AMP production is stimulated by _____.

Answer 18

GMP (GMP needs more ATP to bind to)

Question 19

What is produced first in pyrimidine synthesis?

Answer 19

Carbamoyl phosphate (made by carbamoyl phosphate synthase II)

Question 20

Carbamoyl phosphate is transformed into carbamoyl-aspartate by _________.

Answer 20

ATCase (Aspartate-trascarbamylase)

Question 21

Dihydroorotate is changed to orotate in the _____.

Answer 21

mitochondria

Question 22

Orotate and ____ join to begin the final pyrimidine structure.

Answer 22

PRPP

Question 23

Outline pyrimidine catabolism:

Answer 23

IMP-> Hypoxanthine
Hypoxanthine->xanthine
Xanthine->uric acid