Lecture 9 - Amino Acid Catabolism 2 Flashcards Preview

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Flashcards in Lecture 9 - Amino Acid Catabolism 2 Deck (28)
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1
Q

What does high levels of glutamate cause?

A

Increased water in brain cells through osmosis, causing swelling of the brain leading to a coma

2
Q

What is NH3 converted to and where does the conversion take place?

A
  • Urea

- Liver

3
Q

What do organisms need to have to produce urea from arginine?

A

Arginase

4
Q

What are the 2 compartments of the urea cycle?

A

1) Carbamoyl phosphate acts as a carrier in the mitochondrial matrix
2) NH2 enters the urea cycle in the cytosol through the conversion of ornithine to citrulline

5
Q

What is required to make urea?

A

2 NH3; one from glutamate and one from aspartate

6
Q

Describe the asparate-argininosuccinate shunt

A

Argininosuccinate is split into arginine (which continues the urea cycle) and fumarate (which is converted to malate and then enters TCA cycle)

7
Q

What can deficiencies in urea cycle enzymes lead to?

A
  • Mental retardation (partial deficiency)
  • Early death (mutation in both genes)
  • NH3 build up
8
Q

What can an NH3 buildup cause?

A
  • Activation of glutamate dehydrogenase and glutamine synthetase
  • Loss of ATP (decreases TCA cycle intermediates)
  • Increase in glutamate
9
Q

What is the treatment for a deficiency in urea cycle enzymes?

A

Low protein diet

10
Q

What happens to alpha-keto acids?

A

They are ultimately converted in acetyl CoA that is used in TCA cycle

11
Q

Generally describe the threonine/glycine/serine/alanine pathway

A
  • Threonine is converted to acetyl CoA by 2 pathways
    1) Threonine -> glycine -> serine -> pyruvate -> acetyl CoA
    2) Threonine -> acetaldehyde -> acetate -> acetyl CoA
12
Q

What can a deficiency in acetaldehyde dehydrogenase cause?

A

Alcohol intolerance

13
Q

Which enzymes can convert alanine to pyruvate?

A

Alanine transaminase and alanine dehydrogenase

14
Q

What is FH4?

A
  • Tetrahydrofolate

- Can transfer one carbon in many oxidation states

15
Q

What are the 3 oxidation states of tetrahydrofolate?

A

1) N5, N10-methenyl FH4
2) N5, N10-methylene FH4
3) N5-methy FH4

16
Q

What enzyme converts N5, N10-methenyl FH4 and N5, N10-methylene FH4 between each other and what is the cofactor?

A
  • Methenyl FH4 reductase

- NADH + H+ -> NAD+

17
Q

What enzyme converts N5, N10-methylene FH4 and N5-methy FH4 between each other and what is the cofactor?

A
  • Methylene FH4 reductase

- NADH + H+ -> NAD+

18
Q

What is the function of N5, N10-methenyl FH4?

A

Purine biosynthesis

19
Q

What can N5, N10-methylene FH4 act on?

A

Purines, pyrimidines, and amino acids

20
Q

What can N5-methy FH4 act on?

A

Amino acids

21
Q

Generally describe the phenylalanine/tyrosine pathway

A

Phenylalanine is converted to tyrosine, which is then converted to acetyl CoA by either acetoacetate or fumarate

22
Q

How is fumarate converted to acetyl CoA?

A

Fumarate -> malate -> oxaloacetate -> pyruvate -> acetyl CoA

23
Q

What is phenylketonuria?

A

A genetic disease in which phenylalanine hydroxylase enzyme is absent, therefore the body is unable to metabolize phenylalanine to tyrosine

24
Q

What occurs in phenylketonuria instead of phenylalanine metabolism?

A

Phenylalanine is transaminated to phenylpyruvate, which accumulates in the blood and is excreted in the urine

25
Q

Why are phenylalanine and phenylpyruvate harmful?

A
  • They interfere with normal brain and nerve cell development
  • Phenylalanine competes with other amino acids for uptake in the brain
26
Q

What can elevated phenylalanine levels cause?

A

Lighter skin colour because the increased phenylalanine inhibits melanin synthesis from tyrosine

27
Q

Which enzyme converts tyrosine to melanin?

A

Tyrosinase

28
Q

What can phenylpyruvate be converted to?

A

Phenylacetate or phenyllactate