chapter 32: nucleotide metabolism

nucleoside

consists of nitrogenous base + sugar

purine

2 rings; adenine & guanine

pyrimidine

1 ring; thymine/uracil, cytosine

nucleotide

nitrogenous base, sugar, and phosphate

de novo synthesis

the base itself is synthesized from simpler starting materials, including amino acids; ATP required

salvage pathway

nucleotides are made by recycling bases or nucleosides from degraded DNA/RNA. a base is attached to a ribose, activated in the form of PRPP

bicarbonate, aspartic acid, and ammonia

precursors of pyrimidine rings

carbamoyl phosphate, aspartate

The C2 and N3 atoms in the pyrimidine ring come from ____________, whereas the other atoms of the ring come from ___________.

-

draw out de novo pathway for pyrimidine nucleotide synthesis

glycine, glutamine, aspartate, CO2, tetrahydrofolate

precursors for purine nucleotide synthesis

tetrahydrofolate

Synthesis of purines depends on ___________, a prominent carrier of activated one-carbon units

inosine monophosphate (IMP)

AMP and GMP are formed from

ribonucleotide reductase

reduces ribonucleotides into deoxyribonucleotides

Aspartate transcarbamoylase (ATCase)

a key enzyme for regulation of pyrimidine biosynthesis in bacteria

CTP, ATP

ATCase is inhibited by ____, the final product of pyrimidine biosynthesis, and stimulated by _____