Nitrogen metabolism

Question 1

Essential amino acids

Answer 1

• 10: PVT TIM HALL
• Phenylalanine
• Valine
• Threonine
• Tryptophan
• Isoleucine
• Methionine
• Histidine
• Arginine
• Leucine
• Lysine

Question 2

Nonessential AA

Answer 2

• 11
• Alanine
• Asparagine
• Aspartate
• Cysteine (made from M)
• Glutamate
• Glutamine
• Glycine
• Proline
• Serine
• Tyrosine (Made from F)

Question 3

Hartnup’s disease

Answer 3

• Defect in transport for neutral and aromatic amino acids (including tryptophan)
• Symptoms: pellagra (niacin deficiency: Diarrhea, dermatitis, dementia, death)
• Treatment: administer niacin (B3)
• Diagnosis: pellagra symptoms with neutral and aromatic AA in urine and feces

Question 4

Cytinuria

Answer 4

• Defect in transport for basic amino acids and cystine
• Symptoms: Cystine crystals causing UTIs and kidney stones
• Treatment: Fluids and administration of penicillamine (makes cystine more soluble)

Question 5

Measure of protein breakdown

Answer 5

-3 methyl histidine in urine

Question 6

Catabolism of AA

Answer 6

• Into urea and CO2

- Never turned off but reduced during starvation

Question 7

Amino acid degradation reactions

Answer 7

• 3 main reactions
• Glutamate dehydrogenase (alpha KGglutamate)
• Glutamine synthase (reversible by glutaminase) (glutamateglutamine)
• Carbamoyl phosphate synthase I and II (in mito for urea cycle and cytoplasm for pyrimidine nucleotide biosynthesis)

Question 8

Metabolism of amino-acid derived nitrogen–transamination

Answer 8

• Transaminases (uses pyridoxal phosphate)
• Transfer of amino group from AA to an alpha-ketoacid
• Most transaminases converge on glutamate

Question 9

Oxidative deamination by glutamate dehydrogenase

Answer 9

• Mitochondria
• Alpha KG to glutamate
• NAD or NADP as cofactor

Question 10

Urea cycle

Answer 10

• Carbamoylphosphate (formed from ammonia and CO2 by carbamoylphosphate synthetase, requires 2ATP)
• Citrullline formed by carbamoylphosphate and ornithine catalyzed by OTC (x linked gene, common defect)
• Argininosuccinate formed from citrulline and aspartate via argininosuccinate synthetase (one ATP)
• Arginine and fumarate formed from cleavage of argininosuccinate via argininosuccinate lyase
• Urea and ornithine formed from cleavage of arginine via arginase