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Biochem 2 > Lecture 8 - Amino Acid Catabolism > Flashcards

Lecture 8 - Amino Acid Catabolism Flashcards

1
Q

Which enzymes cleave peptide bonds?

A

Proteases

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2
Q

Are amino acids stored?

A

Nope

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3
Q

What is the purpose of amino acid metabolism?

A

To get the nitrogen out of the amino acid and into urea for excretion

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4
Q

In general terms, what is the first step of amino acid catabolism?

A

Removal of the amino group from the carbon skeleton by transamination and deamination

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5
Q

What happens to the amino group of an amino acid in the liver?

A

Amino groups are transferred to alpha-ketoglutarate, which converts the amino acid to a ketoacid and the alpha-ketoglutarate to glutamate

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6
Q

_____ and _____ are converted to glutamate in the liver

A

Alanine and glutamine

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7
Q

Where are alanine and glutamine degraded?

A

Muscle and other tissues

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8
Q

Define transamination

A

Transferring the NH3 group from an amino acid to a ketoacid

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9
Q

What does transamination require?

A

Pyridoxal phosphate (PLP)

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10
Q

Define deamination

A

Removal of the NH3 group, generating free NH3

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11
Q

What accompanies deamination?

A

Redox reaction using NAD or NADP

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12
Q

Which molecules are always involved in transamination reactions?

A

Glutamate and alpha-ketoglutarate

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13
Q

What is the enzyme that is used in transamination reactions?

A

(Name of amino acid being converted) transaminase

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14
Q

What is the delta G value of transaminase reactions and what does this mean?

A
  • delta G = 0

- They are fully reversible

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15
Q

What is significant about the structure of pyridoxal phosphate?

A

The pyridine ring allows for movement of electrons from NH+

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16
Q

Where is pyridoxal phosphate attached to the enzyme and when is it released?

A
  • Attached at lysine

- Released for reaction to occur

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17
Q

Which amino acid is most commonly deaminated?

A

Glutamate

18
Q

Which enzyme is involved in the deamination of glutamate?

A

Glutamate dehydrogenase

19
Q

Which cofactors are needed for the deamination of glutamate?

A

NAD+ + H2O -> NADH + H+

20
Q

What is produced in the deamination of glutamate?

A

Alpha-ketoglutarate

21
Q

Is the deamination of glutamate reversible?

A

Yes

22
Q

Which enzyme is involved in the deamination of alanine?

A

Alanine dehydrogenase

23
Q

Which cofactors are needed for the deamination of alanine?

A

NAD+ + H2O -> NADH + H+

24
Q

What is produced in the deamination of alanine?

A

Pyruvate and NH3

25
Q

What is involved in an amino acid oxidase?

A

Amino acid is converted to an alpha-ketoacid

26
Q

What are the cofactors needed in an amino acid oxidase reaction?

A

O2 + H2O -> NH3 + H2O2

27
Q

What occurs in the most common deamination route?

A

Transamination is used to generate glutamate, and then glutamate undergoes deamination

28
Q

Describe the deamination of aspartate

A
  • Non-oxidative
  • Enzyme used is asparate alpha-deaminase
  • Produces fumarate and NH3
29
Q

Describe the deamination of serine

A
  • Non-oxidative
  • Enzyme used if serine dehydratase
  • Produces pyruvate and NH3
30
Q

What is produced from oxidative deamination in muscle?

A

Ammonia

31
Q

What does transamination of amino acids in muscle cause?

A

Buildup of glutamate

32
Q

What is the function of glutamine in the blood?

A

Principle carrier of excess NH4

33
Q

How is glutamate converted to glutamine?

A
  • Enzyme is glutamine synthetase

- Cofactors are NH3 in and ATP -> ADP + Pi

34
Q

How is glutamine converted to glutamate?

A
  • Enzyme is glutaminase

- Cofactor is H2O -> NH4+

35
Q

What happens to the released NH4?

A

Enters the urea cycle

36
Q

_____ is the main route for the removal of NH4 from glutamate

A

Glutamate dehydrogenase

37
Q

____ is a secondary NH4 carrier

A

Alanine

38
Q

Where does alanine transport NH4?

A

From muscle to liver

39
Q

_____ is the main route for the removal of NH4 from alanine

A

Alanine dehydrogenase

40
Q

What happens to excess NH3?

A

Converted to urea and excreted

41
Q

Why is NH3 harmful?

A

High [NH3] activates glutamate dehydrogenase/glutamine synthetase, producing glutamate and glutamine, which uses up ATP/NADH and can be damaging to the brain

Biochem 2 (40 decks)

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