Nucleotide Synthesis

Question 1

What regulates the activity of glutamine-PRPP amidotransferase?

Answer 1

Inhibited by AMP, GMP, and IMP

Question 2

What regulates adenylosuccinate synthetase?

Answer 2

AMP inhibits it

Question 3

What regulates IMP dehydrogenase?

Answer 3

GMP inhibits it

Question 4

What regulates the activity of PRPP synthetase?

Answer 4

ADP inhibits it

Question 5

Major enzyme and reactions in purine nucleotide salvage pathways

Answer 5

HGPRT;
PRPP+guanine–>GMP
PRPP+hypoxanthine–> IMP

Question 6

Minor salvage pathway?

Answer 6

PRPP+adenine–> AMP via adenine phosphoribosyltransferase (APRT)

Question 7

What are the precursors for pyrimidine nucleotide synthesis?

Answer 7

R5P, CO2, Gln, and Asp

Question 8

What is the rate limiting step in pyrimidine synthesis?

Answer 8

Conversion of Gln+2ATP+HCO3–> carbamoyl phosphate + 2ADP + Pi + Glu; synthesized by CPS II

Question 9

Compare the metabolic process, location, nitrogen donor, and regulatory effectors of CPS I and CPS II

Answer 9

Metabolic: CPS I–> urea synthesis; CPS II–> pyrimidine biosynthesis

Location: CPS I–> mitochondrial matrix; CPS II–> cytosol

N donor: free ammonium; glutamine

Regulatory effectors: (+) N-acetylglu and (+) Arginine; (-) UTP and (+) ATP and PRPP

Question 10

What reaction does aspartame transcarbamoylase catalyze?

Answer 10

The conversion of aspartate and carbamoyl phosphate to N-carbamoylaspartate