Amino Acid Metabolism

Question 1

How is citruline turned into arginine?

Answer 1

citruline -> argino-succinate synthetase -> arginino succinate -> arginine

Question 2

How does arginine convert into nitric oxide?

Answer 2

using NOS

Question 3

What is arginine a precursor for?

Answer 3

• polyamines -> ornithine, putrescine, spermidine, spermine
• creatine, creatine phosphate, creatinine
• nitric oxide, glutamate, urea

Question 5

What are the precursors to glutamate?

Answer 5

• histidine
• proline
• arginine

Question 6

What enzymes & cofactors are needed for phenylalanine -> tyrosine?

Answer 6

THBiopterin, phenylalanine hydroxylase, & O2

Question 7

What are the precursor of catecholamines?

Answer 7

Phe/Tyr

Question 8

What pigments relate to pheomelanins & eumelanins?

Answer 8

• pheo -> red pigments
• eumel -> black pigments

Question 9

What happens if tyrosinase is inhibited?

Answer 9

causes albinism

Question 10

What happens if PKU is inhibited?

Answer 10

phenylalanine doesn’t go to tyrosine

Question 11

What are Phe/Tyr precursors for?

Answer 11

• catecholamines: dopamine, norepinephrine, epinephrine
• melanin
• thyroid hormones: T3, rT3, T4

Question 12

What is tryptophan a precursor to?

Answer 12

• serotonin
• nicotinate
• melatonin

Question 13

What are the enzymes needed for decarboxylation?

Answer 13

glutamate decarboxylase & histidine decarboxylase

Question 14

What is albinism?

Answer 14

Deficiency in Tyrosinase = no melanin production

Question 15

What is Parkinson’s disease?

Answer 15

• Dopamine deficiency in the brain
• treatment: carbidopa

Question 16

What is PKU disorder?

Answer 16

• phenylalanine interferes with the hydrophobic amino acid transport across the blood brain barrier
• thus an increase in phenylpyruvic acids contributes to the lack of myelin production