nucleotide catabolism and salvage Flashcards
how many broad pathways are involved in the biosynthesis of nucleotides
two
name the 2 pathways involved in the biosynthesis of nucleotides
de novo synthesis and salvage pathway
what is de novo synthesis
synthesizes nucleotides from their metabolic precursoers (amino acids, CO2, NH3)
what is the salvage pathway
recycle free bases and nucleotides relased from the nucleic acid catabolism
when does nucleotide synthesis occur
during nucleic acid synthesis
describe the first step of nucleotide synthesis
purine and pyrimide nucleotides are synthesised to the monophosphorylated ribonucleotides. The purine ring is sequentially built before it is attached to the phosphorylated ribose. the pyrimide ring is synthesised before it is attached to the phosphorylated ribose
describe the second step of nucleotide synthesis
the monophosphates are converted to the triphosphates
describe the third step of nucleotide synthesis
deoxyribonucleotides are syntheised from the ribnucleotides
describe the fourth step of nucleotide synthesis
thymidylate is syntheised from deoxyribouridine
how does de novo synthesis start
the donation of an amino group on glutamine to the c-1 of phosphoribosyl pyrophosphate (PRPP) to form 5-phosphoribosylamine
what is the purine ring structure built on
5-phosphoribosylamine
what does the purine ring structure being built on 5-phosphoribosylaime result in
inosine-5/-monophosphate (IMP) through amino-transfase and transformylation reactions
what is consumed during IMP synthesis
5 x ATP
glutamine, glycine and asparate as nitrogen donors
2 x formate
what is IMP
a branch point in purine biosynthesis
how is IMP connected to AMP and GMP
AMP and GMP are both dervived from IMP through 2 pathways
