Lecture 14 - Amino Acid Synthesis

Question 1

What process(es) provide the carbon skeleton for amino acids?

Answer 1

Glycolysis and TCA cycle

Question 2

How many amino acids can bacteria/plants make?

Answer 2

All 20

Question 3

How many amino acids can mammals make?

Answer 3

About 10

Question 4

Which amino acids are essential amino acids (ones that the body cannot produce)?

Answer 4

1) Histidine
2) Valine
3) Leucine
4) Isoleucine
5) Tryptophan
6) Phenylalanine
7) Methionine
8) Threonine
9) Lysine
10) Arginine

Question 5

Which hormones are derived from amino acids?

Answer 5

Dopamine and epinephrine, which both derive from tyrosine (tyrosine -> dopamine -> epinephrine)

Question 6

What is Parkinson’s and how can it be treated?

Answer 6

• Insufficient formation and action of dopamine

- Treated with a dopamine precursor (L-DOPA)

Question 7

What is histamine derived from?

Answer 7

Histidine

Question 8

What is seratonin derived from?

Answer 8

Tryptophan

Question 9

What is the difference between nucleosides and nucleotides?

Answer 9

Nucleosides have a sugar and a base, while nucleotides have a sugar, a base, and one or more phosphates

Question 10

What is sulphonation?

Answer 10

Conversion of cytosine to cytosinsulphonate

Question 11

What is the site of methylation during sulphonation?

Answer 11

The double bond of cytosine

Question 12

What is desulphonation?

Answer 12

Conversion of uracilsulphonate to uracil

Question 13

What molecules are needed for hydrolytic deamination?

Answer 13

H2O and NH4+

Question 14

What are the pKa values of the oxygens of a phosphate in a nucleotide?

Answer 14

From 1-6, so they are ionized at pH 7

Question 15

Do purines or pyrimidines have two rings?

Answer 15

Purines

Question 16

Thymine is found in _____, while uracil is found in ____

Answer 16

DNA; RNA

Question 17

What are the 2 pathways for nucleotide synthesis?

Answer 17

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

Question 18

Where do the carbons and nitrogens of a purine come from?

Answer 18

• 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

Question 19

Nucleotides are synthesized in the _____ form

Answer 19

Ribose

Question 20

How are deoxyribose molecules made?

Answer 20

A ribose is reduced by ribonucleoside diphosphate reductase using thioredoxin

Question 21

What is the cofactor of the conversion of a nucleoside diphosphate to a deoxynucleoside diphosphate, and what is this cofactor coupled to?

Answer 21

• Thioredoxin SH-SH -> thioredoxin S-S

- The reverse reaction is coupled to NADPH + H+ -> NADP+

Question 22

What is another name for ribonucleoside diphosphate reductase?

Answer 22

Ribonucleotide reductase

Question 23

What molecule and enzyme does deoxythymidine synthesis use that is unique?

Answer 23

dUMP and thymidylate synthase

Question 24

Step 1 of deoxythymidine synthesis

Answer 24

dUMP -> dTMP

Question 25

Enzyme of step 1 of deoxythymidine synthesis

Answer 25

Thymidylate synthase

Question 26

Cofactor of step 1 of deoxythymidine synthesis

Answer 26

FH4-CH2OH -> FH2

Question 27

Step 2 of deoxythymidine synthesis

Answer 27

FH2 -> FH4

Question 28

Enzyme of step 2 of deoxythymidine synthesis

Answer 28

Dihydrofolate reductase

Question 29

Cofactor of step 2 of deoxythymidine synthesis

Answer 29

NADH + H+ -> NAD+

Question 30

Step 3 of deoxythymidine synthesis

Answer 30

FH4 -> FH4-CH2OH

Question 31

Enzyme of step 3 of deoxythymidine synthesis

Answer 31

Serine hydroxymethyl transferase

Question 32

Cofactor of step 3 of deoxythymidine synthesis

Answer 32

Serine -> glycine

Question 33

What inhibits thymidylate synthase and how does it do this?

Answer 33

• FdUMP, which originates as fluoruracil

- Forms a stable complex between the enzyme and FH4