Introduction to Amino Acid Metabolism

Question 1

Name some specialised moleucles derived from amino acids

Answer 1

Hormones
Vitamins
Pigments
Nitric oxide
Glutathione
Phosphocreatine
Neurotransmitters

Question 2

Which amino acid is a precursor for thyroxine?

Answer 2

Tyrosine

Question 3

What amino acid is a precursor to niacin (NAD/NADP)?

Answer 3

Tryptophan

Question 4

What amino acid is used to make ALA, a haem precursor?

Answer 4

Glycine

Question 5

How is nitric oxide synthesised in host defence?

Answer 5

From arginine by iNOS

Question 6

Which three amino acids are precursors of glutathione?

Answer 6

Cysteine
Glutamate
Glycine

Question 7

What is phosphocreatine made from?

Answer 7

Arginine
Glycine
Methionine

Question 8

Which neurotransmitter is derived from glutamate?

Answer 8

GABA

Question 9

What is GABA’s function?

Answer 9

Inhibitory neurotransmitter; underproduction is linked to epilepsy

Question 10

How does diazepam (Valium) affect GABA receptors?

Answer 10

Binds allosterically, enhancing GABA binding –> reduces neuron firing

Question 11

What compound is formed from histidine?

Answer 11

Histamine

Question 12

What is histamine’s function in the body?

Answer 12

Acts as a vasodilator; involved in allergic responses

Question 13

What type of drugs coneract histamine effects?

Answer 13

Antihistamines

Question 14

What enxyme is deficient in classical PKU?

Answer 14

Phenylalanine hydroxylase (PAH)

Question 15

What cofactor does PAH use?

Answer 15

Tetrahydrobiopterin (BH4)

Question 16

What are the consequences of untreated PKU?

Answer 16

Brain damage
Seizures
Impaired neurotransmitter synthesis

Question 17

How is PKU detected?

Answer 17

Blood amino acid measurement using tandem mass spectrometry

Question 18

What is atypical PKU casued by?

Answer 18

BH4 deficiency

Question 19

What other neurotransmitters require BH4 for synthesis?

Answer 19

Epinepherine and serotonin

Question 20

What is a dietary treatment for BH4 - deficient PKU?

Answer 20

Supplement with DOPA and 5-hydroxytryptophan

Question 21

How does phenylalanine ammonia lyase treat PKU?

Answer 21

Converts phenylalanine to cinnamic acid for excretion

Question 22

List the major roles of nucleotides

Answer 22

DNA/RNA building blocks
Energy carries (ATP/GTP)
Cofactors (NAD/FAD)
Second messengers (cGMP)

Question 23

What is the de novo nucleotide synthesis pathway made from?

Answer 23

Amino acids
Ribose 5-phosphate
CO2
NH3

Question 24

What is the purine salvage enzyme?

Answer 24

Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)

Question 25

What causes Lesch-Nyhan Syndrome?

Answer 25

HGPRT1 gene defect (X-linked)

Question 26

What are key symptoms of Lesch-Nyhan Syndrome?

Answer 26

Mental retardation Aggression Kidney issues Gout-like symptoms

Question 27

Why is the brain especially affected in Lesch-Nyhan?

Answer 27

It depends heavily on purine salvage

Question 28

What condition results from TYMP gene defects?

Answer 28

Mitochondrial Neurogastrointestinal Encephalomyopathy

Question 29

Symptoms of MNE?

Answer 29

Mitochondrial depletion GI issues Neuropathies

Question 30

What enzymes breaks down uracil and thymine?

Answer 30

Dihydropyrimidine dehydrogenase (DPD/DPYD)

Question 31

What results from DPD deficiency?

Answer 31

Seizures Intellectual disability Microcephaly Hypertonia Drug sensitivity

Question 32

List the steps in AMP degredation

Answer 32

AMP --> adenosine --> inosine --> hypoxanthine --> xanthine --> uric acid

Question 33

List the steps in GMP degradation

Answer 33

GMP --> guanosine --> guanine --> xanthine --> uric acid

Question 34

What causes gout?

Answer 34

Uric acid build up from purine degredation

Question 35

Why are humans prone to gout?

Answer 35

Evolutionary loss of urate oxidase

Question 36

Symptoms of gout?

Answer 36

Joint pain Kidney issues

Question 37

What can casue genetic gout?

Answer 37

Defects in an ABC transporter for urate excretion

Question 38

Lifestyle changes to manage gout?

Answer 38

Limit meat, alcohol, fructose Increase vitamin C Avoid obesity

Question 39

What is allopurinol?

Answer 39

Xanthine oxidase inhibitor that reduces uric acid formation

Question 40

How doe allopurinol work?

Answer 40

Mimic hypoxanthine; converted to oxypurinol, block enzyme activity --> more xanthine/hypoxanthine (water-soluble, excretable_