Amino Acid Catabolism

Question 1

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

Answer 1

1. Ammonia
2. Urea
3. TCA cycle intermediates

Question 2

3 disposal methods of body nitrogen?

Answer 2

Transamination, deamination, and transport of ammonia

Question 3

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)

Answer 3

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

Question 4

Transamination is done by a family of enzymes called

Where are these enzymes located

How are these enzymes named?

Answer 4

Amino transferase/transaminase

In cytsol/mitochondria of liver, and muscle

After the specific amino group donor

Question 5

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

What enzyme does this?

Answer 5

Pyruvate (keto acid) and glutamate (amino acid)

ALT

Question 6

What does aspartic acid + alpha ketoglutarate transaminate to?

What enzyme does this

Answer 6

Oxaloacetate and glutamate

AST

Question 7

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

Answer 7

Glutamate (and acceptor group is almost always alpha ketoglutarate)

Question 8

Why are ALT and AST used for diagnosis?

Answer 8

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

Question 9

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

Answer 9

Non hepatic diseases (MI and muscle disorders)

Question 10

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

Answer 10

Hepatic diseases

Question 11

Are these transamination reactions reversible?

Answer 11

Yes

Question 12

Deamination:

1. Function of this type of reaction?
2. Oxidative deamination is done by which enzyme
3. Reversible?
4. Location?

Answer 12

1. Removal of amino group as ammonia
2. Glutamate dehydrogenase
3. Yes
4. Mitochondrial matrix of the liver and kidney

Question 13

What is the only amino acid that undergoes rapid oxidative deamination

Answer 13

Glutamate

Question 14

Result of oxidative deamination

Answer 14

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

Question 15

1. Disposal of amino acids is called ___

2. Synthesis of amino acids is called __

Answer 15

1. Oxidative deamination
2. Reductive amination

~same process just reversed

Question 16

Nitrogen mainly travels in which two amino acids?

Answer 16

Alanine and glutamine

Question 17

1. Glutamine transports ammonia from __ to __

2. Alanine transports ammonia from __ to __

Answer 17

1. Peripheral tissue to liver

2. Muscle to liver

Question 18

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?

Answer 18

1. Glutamine synthase
2. Glutamine to glutamate by glutaminase
3. Releases ammonia to liver

Question 19

What is the best carrier of ammonia group?

Answer 19

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

Question 20

Glutamine transport is major mechanism for detoxification of?

Answer 20

Ammonia in the brain

Question 21

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

Answer 21

Excrete ammonia

Question 22

Source of NH3 in the intestine?

Answer 22

Bacterial flora

Question 23

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

Answer 23

1. Kidneys
2. Excreted in the urine has NH4+
3. Maintaining acid base balance of the body

Question 24

What ion can be exchanged for NH4+

What does this help with

When would this be handy?

Answer 24

H+

Acid base balance

When you are in acidosis or alkalosis

Question 25

Glutamate in liver gets excreted as? Glutamate in kidney gets excreted as? Glutamate in intestine?

Answer 25

Urea Ammonium ion in the urine Enters portal circulation then taken to the liver to form urea

Question 26

Source of glutamine in the intestine?

Answer 26

Proteolysis of dietary protein

Question 27

Urea cycle: 1. Location of synthesis of urea? 2. Urea clearance is a measure of? 3. Urea is soluble in? 4. Mammals are primarily

Answer 27

1. Cytosol and mitochondria of the liver 2. Glomerular filtration rate (GFR) 3. Water 4. Ureotelic - producing urea, not uric acid

Question 28

Main function of urea?

Answer 28

To get rid of ammonia

Question 29

What is CPS 1 involved in? CPS2?

Answer 29

Urea cycle Nucleotide synthesis

Question 30

Urea cycle requires?

Answer 30

2 ATP

Question 31

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

Answer 31

First-ammonia | Second-aspartate

Question 32

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

Answer 32

Ammonia and CO2 to make carbamoyl phosphate Mg2+

Question 33

What is significant about CPS1? What does CPS1 require?

Answer 33

Rate limiting step Requires an activator (NAG)

Question 34

NAG is synthesized from? What does NAG do to activate CPS1?

Answer 34

Acetyl CoA and glutamate by NAG synthase Enhances its affinity for ATP

Question 35

When will intrahepatic concentration of NAG increase?

Answer 35

After a protein rich meal

Question 36

Second step of urea cycle: __ and __ combine to form __ by which enzyme?

Answer 36

Carbamoyl phosphate combines with ornithine to form citrulline by OTC

Question 37

What does oral neomycin administration do?

Answer 37

Reduces intestinal bacteria - decreased NH3

Question 38

In renal failure patients, what enzyme works on urea?

Answer 38

Urease (important source of NH3 in feces) ~so check for release of urea to determine if there is kidney dysfunction

Question 39

Normal ammonia level How much to be considered hyperammonemia ?

Answer 39

5-50 mmol/L 1000 mmol/L or more

Question 40

Signs of hyperammonemia

Answer 40

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

Question 41

Main causes of hyperammonemia What does it cause?

Answer 41

Liver disease (cirrhosis), toxic mushrooms, alcoholism, biliary obstruction ~so anything that affects the liver Causes increased levels of circulating ammonia

Question 42

Hereditary hyperammonemia 1. Deficiency in what enzymes 2. Treatment?

Answer 42

1. Either CPS1 (type 1) or OTC (type 2) | 2. Limiting protein in diet/ pheyl butyrate

Question 43

Difference between CPS 1 deficiency and OTC deficiency presentation

Answer 43

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