Lecture 14 - Amino Acid Synthesis Flashcards
What process(es) provide the carbon skeleton for amino acids?
Glycolysis and TCA cycle
How many amino acids can bacteria/plants make?
All 20
How many amino acids can mammals make?
About 10
Which amino acids are essential amino acids (ones that the body cannot produce)?
1) Histidine
2) Valine
3) Leucine
4) Isoleucine
5) Tryptophan
6) Phenylalanine
7) Methionine
8) Threonine
9) Lysine
10) Arginine
Which hormones are derived from amino acids?
Dopamine and epinephrine, which both derive from tyrosine (tyrosine -> dopamine -> epinephrine)
What is Parkinson’s and how can it be treated?
- Insufficient formation and action of dopamine
- Treated with a dopamine precursor (L-DOPA)
What is histamine derived from?
Histidine
What is seratonin derived from?
Tryptophan
What is the difference between nucleosides and nucleotides?
Nucleosides have a sugar and a base, while nucleotides have a sugar, a base, and one or more phosphates
What is sulphonation?
Conversion of cytosine to cytosinsulphonate
What is the site of methylation during sulphonation?
The double bond of cytosine
What is desulphonation?
Conversion of uracilsulphonate to uracil
What molecules are needed for hydrolytic deamination?
H2O and NH4+
What are the pKa values of the oxygens of a phosphate in a nucleotide?
From 1-6, so they are ionized at pH 7
Do purines or pyrimidines have two rings?
Purines
Thymine is found in _____, while uracil is found in ____
DNA; RNA
What are the 2 pathways for nucleotide synthesis?
1) De novo pathway - made from scratch using ribose ring as a scaffold
2) Salvage pathway - recycling of free bases and nucleosides released from nucleic acid breakdown
Where do the carbons and nitrogens of a purine come from?
- One N from aspartate
- One C from CO2
- C=C-N from glycine
- Two C’s from formate (FH4)
- Two N’s from amide nitrogen of glutamine
Nucleotides are synthesized in the _____ form
Ribose
How are deoxyribose molecules made?
A ribose is reduced by ribonucleoside diphosphate reductase using thioredoxin
What is the cofactor of the conversion of a nucleoside diphosphate to a deoxynucleoside diphosphate, and what is this cofactor coupled to?
- Thioredoxin SH-SH -> thioredoxin S-S
- The reverse reaction is coupled to NADPH + H+ -> NADP+
What is another name for ribonucleoside diphosphate reductase?
Ribonucleotide reductase
What molecule and enzyme does deoxythymidine synthesis use that is unique?
dUMP and thymidylate synthase
Step 1 of deoxythymidine synthesis
dUMP -> dTMP
Enzyme of step 1 of deoxythymidine synthesis
Thymidylate synthase
Cofactor of step 1 of deoxythymidine synthesis
FH4-CH2OH -> FH2
Step 2 of deoxythymidine synthesis
FH2 -> FH4
Enzyme of step 2 of deoxythymidine synthesis
Dihydrofolate reductase
Cofactor of step 2 of deoxythymidine synthesis
NADH + H+ -> NAD+
Step 3 of deoxythymidine synthesis
FH4 -> FH4-CH2OH
Enzyme of step 3 of deoxythymidine synthesis
Serine hydroxymethyl transferase
Cofactor of step 3 of deoxythymidine synthesis
Serine -> glycine
What inhibits thymidylate synthase and how does it do this?
- FdUMP, which originates as fluoruracil
- Forms a stable complex between the enzyme and FH4
