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Biochemistry Block 3 > Amino Acid Catabolism > Flashcards

Amino Acid Catabolism Flashcards

1
Q

Amino acid catabolism includes:

  1. Removal of alpha amino group as
  2. Converion of ammonia into
  3. Conversion of remaining amino acids carbon skeleton into
A
  1. Ammonia
  2. Urea
  3. TCA cycle intermediates
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2
Q

3 disposal methods of body nitrogen?

A

Transamination, deamination, and transport of ammonia

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3
Q

Transamination:

  1. What is happening?
  2. So acceptor of amino group is?
  3. Is ammonia released?
    * 4. Requires?
  4. 3 exceptions (do not go through transamination)
A
  1. Transfer of amino group from an amino acid to keto acid to form a newer keto acid and newer amino acid respectively
  2. Keto acid
  3. No
    * 4. Pyridoxal phosphate (vitamin B6)(PLP)
  4. Lysine, threonine, and proline ~sometimes proline does
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4
Q

Transamination is done by a family of enzymes called

Where are these enzymes located

How are these enzymes named?

A

Amino transferase/transaminase

In cytsol/mitochondria of liver, and muscle

After the specific amino group donor

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5
Q

Alanine + alpha ketoglutarate transaminate to give you what two things?

What enzyme does this?

A

Pyruvate (keto acid) and glutamate (amino acid)

ALT

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6
Q

What does aspartic acid + alpha ketoglutarate transaminate to?

What enzyme does this

A

Oxaloacetate and glutamate

AST

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7
Q

All the amino nitrogens that undergo transamination can be concentrated in?

A

Glutamate (and acceptor group is almost always alpha ketoglutarate)

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8
Q

Why are ALT and AST used for diagnosis?

A

They are nonfunctional enzymes which are not supposed to be present in the blood - if they are, then you know there is a pathology

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9
Q

If serum AST is more specific than ALT, what diagnosis does that indicate

A

Non hepatic diseases (MI and muscle disorders)

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10
Q

If serum ALT is more specific than serum AST, what diagnosis does that indicate?

A

Hepatic diseases

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11
Q

Are these transamination reactions reversible?

A

Yes

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12
Q

Deamination:

  1. Function of this type of reaction?
  2. Oxidative deamination is done by which enzyme
  3. Reversible?
  4. Location?
A
  1. Removal of amino group as ammonia
  2. Glutamate dehydrogenase
  3. Yes
  4. Mitochondrial matrix of the liver and kidney
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13
Q

What is the only amino acid that undergoes rapid oxidative deamination

A

Glutamate

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14
Q

Result of oxidative deamination

A

Release of a free ammonium ion (but body has to get rid of this or it can be toxic)

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15
Q
  1. Disposal of amino acids is called ___

2. Synthesis of amino acids is called __

A
  1. Oxidative deamination
  2. Reductive amination

~same process just reversed

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16
Q

Nitrogen mainly travels in which two amino acids?

A

Alanine and glutamine

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17
Q
  1. Glutamine transports ammonia from __ to __

2. Alanine transports ammonia from __ to __

A
  1. Peripheral tissue to liver

2. Muscle to liver

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18
Q
  1. In most of the tissues, glutamate gets converted to glutamine by which enzyme?
  2. What happens in liver, kidney, and intestine and by which enzyme?
  3. Glutaminase also does what?
A
  1. Glutamine synthase
  2. Glutamine to glutamate by glutaminase
  3. Releases ammonia to liver
19
Q

What is the best carrier of ammonia group?

A

Glutamine - gets synthesized in most tissues then gets carried to liver/kidney/intestine where glutaminase works on it

20
Q

Glutamine transport is major mechanism for detoxification of?

A

Ammonia in the brain

21
Q

Liver, kidney, and intestine are only tissues that can?

A

Excrete ammonia

22
Q

Source of NH3 in the intestine?

A

Bacterial flora

23
Q
  1. Glutamine is removed from circulation by?
  2. What happens to most of the ammonia from when glutamine is converted to glutamate
  3. What is this mechanism important for
A
  1. Kidneys
  2. Excreted in the urine has NH4+
  3. Maintaining acid base balance of the body
24
Q

What ion can be exchanged for NH4+

What does this help with

When would this be handy?

A

H+

Acid base balance

When you are in acidosis or alkalosis

25
Q

Glutamate in liver gets excreted as?

Glutamate in kidney gets excreted as?

Glutamate in intestine?

A

Urea

Ammonium ion in the urine

Enters portal circulation then taken to the liver to form urea

26
Q

Source of glutamine in the intestine?

A

Proteolysis of dietary protein

27
Q

Urea cycle:

  1. Location of synthesis of urea?
  2. Urea clearance is a measure of?
  3. Urea is soluble in?
  4. Mammals are primarily
A
  1. Cytosol and mitochondria of the liver
  2. Glomerular filtration rate (GFR)
  3. Water
  4. Ureotelic - producing urea, not uric acid
28
Q

Main function of urea?

A

To get rid of ammonia

29
Q

What is CPS 1 involved in?

CPS2?

A

Urea cycle

Nucleotide synthesis

30
Q

Urea cycle requires?

A

2 ATP

31
Q

First amino group (nitrogen) utilized in urea cycle is provided by? Second?

A

First-ammonia

Second-aspartate

32
Q

CPS1 (carbamoyl phosphate synthetase 1) is utilized in the first step of urea cycle. What is it combining?

This reaction requires?

A

Ammonia and CO2 to make carbamoyl phosphate

Mg2+

33
Q

What is significant about CPS1?

What does CPS1 require?

A

Rate limiting step

Requires an activator (NAG)

34
Q

NAG is synthesized from?

What does NAG do to activate CPS1?

A

Acetyl CoA and glutamate by NAG synthase

Enhances its affinity for ATP

35
Q

When will intrahepatic concentration of NAG increase?

A

After a protein rich meal

36
Q

Second step of urea cycle:

__ and __ combine to form __ by which enzyme?

A

Carbamoyl phosphate combines with ornithine to form citrulline by OTC

37
Q

What does oral neomycin administration do?

A

Reduces intestinal bacteria - decreased NH3

38
Q

In renal failure patients, what enzyme works on urea?

A

Urease (important source of NH3 in feces)

~so check for release of urea to determine if there is kidney dysfunction

39
Q

Normal ammonia level

How much to be considered hyperammonemia ?

A

5-50 mmol/L

1000 mmol/L or more

40
Q

Signs of hyperammonemia

A

Very sleepy during the day, flapping tremors, liver enlargement, SOB, papilledema (eyes), rigid trunk, and loss of coordination

~so CNS involvement

41
Q

Main causes of hyperammonemia

What does it cause?

A

Liver disease (cirrhosis), toxic mushrooms, alcoholism, biliary obstruction

~so anything that affects the liver

Causes increased levels of circulating ammonia

42
Q

Hereditary hyperammonemia

  1. Deficiency in what enzymes
  2. Treatment?
A
  1. Either CPS1 (type 1) or OTC (type 2)

2. Limiting protein in diet/ pheyl butyrate

43
Q

Difference between CPS 1 deficiency and OTC deficiency presentation

A

CPS1 has no increase in orotic acid and uracil, OTC does

Biochemistry Block 3 (11 decks)

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