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Metabolism > 8. Amino Acid Catabolism > Flashcards

8. Amino Acid Catabolism Flashcards

1
Q

What are the preferred fuel sources?

A

carbohydrates and fat

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2
Q

Proteins are not a preferred fuel source. True or false?

A

TRUE

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3
Q

Whether from intracellular protein or dietary protein, what do you need to do to catabolize amino acids?

A

You need to break down amino acid by deamination to remove amino group. This is removed via ammonia release, which must enter the urea cycle. Then convert carbon skeleton into a-keto acids that can be converted to CAC substrates.

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4
Q

Only active when it is _____________, ensuring that damage doesnt occur

A

stomach

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5
Q

_____________ and _____________ is produced in pancreas and used in intestine for protein breakdown

A

trypsin

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6
Q

What is the anatomical difference between carnivores and others?

A

Animals that just eat meat, have short intestines, whereas those who digest many carbs, need longer organ to process and absorb

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7
Q

Read over well

A

okay

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8
Q

3 functions of amino acids

A

1.they are monomeric constituents of proteins

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9
Q

Three major steps in the catabolism of AAs. Describe each briefly:

A

There are three major steps in catabolism of AAs.

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10
Q

What is formed in oxidative deamination?

A

In oxidative deamination, nadh (or nadph) and a-ketoglutarate is formed

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11
Q

True or false?

A

TRUE

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12
Q

Describe removal of nh2 group from amino acids

A

Amino group is transferred to a-ketoglutarate becoming glutamate. Remaining amino acid structure forms a-keto acids.

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13
Q

___________ amino removal forms glutamate, which another deamination following the first one makes a-ketoglutarate

A

alanine

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14
Q

Excretory forms of Nitrogen

A

ammonia, urea, uric acid

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15
Q

Provide the transamination reaction of amino acid deamination:

A

a-ketoglutarate + AA –> glutamate and a-keto acid (by aminotransferase and PLP)

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16
Q

Describe transamination of amino acid deamination:

A

Transfer of amino group to a-ketoglutarate. There are several aminotransferases specific to different amino acids. In this step amino group from all the amino acids are transferred to a-ketoglutarate and they exist as glutamate.

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17
Q

When did we last see PLP?

A

PLP was used in glycogen phosphorylase reaction

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18
Q

What is the role of PLP?

A

PLP is converted to pyridoxamine phosphate when it carries an amino group from the amino acid to a-ketoglutarate during transamination

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19
Q

Provide the oxidative deamination reaction:

A

glutamate + h2o –> a-ketoglutarate + nh4+ (by glutamate dehydrogenase and nad+ or nadp+)

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20
Q

What is inhibiting and what is activating oxidative deamination? Why does this makes sense?

A

gtp inhibits (high energy situation, so unnecessary)

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21
Q

Read over well

A

okay

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22
Q

True or false?

A

TRUE

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23
Q

Describe transport of excess ammonia by glutamine:

A

Glutamine synthetase makes glutamine from glutamate

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24
Q

Read over well.

A

okay

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25
Q

So, free ammonia cannot be brought to liver, but glutamate cannot be used either. Why?

A

because it is a neurotransmitter, which can cause problems if transferred through blood.

26
Q

Describe Glucose-Alanine cycle:

A

Amino group from excess glutamate produced in muscle as a result of amino acid catabolism, is transferred to pyruvate resulting in the formation of alanine.

27
Q

True or false?

A

TRUE

28
Q

Describe carbamoyl phosphate synthase-I reaction:

A

Free ammonia not loaded onto HCO3. but if activated by ATP it becomes carbonic phosphoric acid anhydride. Then phosphate can be kicked out and ammonia can hop on.

29
Q

What are the products of the urea cycle?

A

urea and fumarate

30
Q

Name the 5 enzymes of urea cycle:

A
  1. Carbamoyl phosphate synthase
31
Q

Describe urea cycle

A

Bicarbonate and 2 atp with ammonia makes carbamoyl phosphate

32
Q

What happens in brain in presence of high amount of ammonia?

A

Brain doesn’t produce ammonia, but problem with urea cycle can result in blood bringing it to brain.

33
Q

How much a-ketoglutarate is used for every 1 ammonia converted in brain?

A

0.5

34
Q

What are the 2 issues with ammonia detoxification in brain?

A

This is problem 1 –> depletion of a-ketoglutarate –> energy generation inhibition

35
Q

Briefly list the 3 possible therapies for the patients with defect in urea cycle:

A

1.Defined diet containing just the minimum amount of essential amino acids.

36
Q

Explain how defined diet containing just the minimum amount of essential amino acids overcomes urea cycle defects

A

To avoid ammonia toxicity, don’t use protein for energy generation (don’t eat excess amount of protein and eat more carbohydrates and fats)

37
Q

Feeding the patients with Benzoate or phenylacectate. Explain how this solves urea cycle defect:

A

These compound react with glycine and glutamine respectively forming non-toxic compounds that are excreted in urine. Thus the body runs low in glycine and glutamine and starts synthasizing these AA using the ammonia available in system. Thus clearing the system of excess ammonia.

38
Q

In the patients with N-acetylglutamate synthase deficiency, Carbamoyl glutamate can act as activator of carbamoyl phosphate synthase. Explain how this solves issues with urea cycle:

A

By activating carbamoyl phosphate synthase, you can get more urea cycle

39
Q

Describe Regulation of urea cycle: (2)

A

Regulation of urea cycle:

40
Q

Interaction of Urea Cycle and Citric Acid Cycle occurs via what?

A

Aspartate-Argininosuccinate shunt

41
Q

Describe how urea and TCA interact:

A

Urea –> take ornithine, load it with carbamoyl phosphate to form citrulline which goes into cytosol and is joined with aspartic acid to make argininosuccinate, which gets hydrolyzed to form arginine, which is converted to urea and ornithine

42
Q

Describe cofactors in AA metabolism

A

Cofactors are carriers of methyl, amino, methoxy, aldehyde, acidic groups. Can transfer 1 carbon from 1 compound to the other compound.

43
Q

Example of Methyl Group transfer using Tetrahydrofolate as cofactor

A

Tetrahydrofolate transfers methyl group

44
Q

What is the main takeaway from tetrahydrofolate co-factor?

A

tetrahydrofolate can carry carbons in different forms for amino acid metabolism

45
Q

Describe the catabolism of alanine:

A

Alanine: using PLP, ammonia taken away by a-ketoglutarate and alanine becomes pyruvate.

46
Q

Describe the catabolism of threonine:

A

Threonine: using PLP, hydroxymethyl transferase reaction occurs and acetaldehyde comes out, leaving glycine (lost 2 carbons). Acetaldehyde is converted to alcohol which can be converted to acetyl-coa to make energy.

47
Q

Describe the catabolism of glycine:

A

Glycine: one carbon is added to glycine by the methylenefolate to become a serine using serine hydroxymethyl transferase

48
Q

Describe the catabolism of serine:

A

Serine: serine dehydratase converts serine to pyruvate using PLP and ammonia is released.

49
Q

Describe the catabolism of cysteine:

A

Cysteine: 2 steps converted to pyruvate.

50
Q

Tryptophan has ___________ kind of group so it gets converted to ___________ .

A

alanine

51
Q

Describe the metabolic fates of glycine:

A
  1. glycine is converted to co2 and nh4 to make nadh using glycine synthase.
52
Q

Catabolic pathways of Aspartic acid and asparagine

A

Asparagine has 2 amino groups. Asparaginase gets rid of ammonia and becomes aspartic acid. Aspartate aminotransferase uses alpha KG to remove amino group loaded onto glutamate and oxaloacetate forms which can directly participate in CAC.

53
Q

Catabolic pathway for glutamate and glutamine

A

glutamine contains 2 amino groups. Glutaminase removes an amino group to make glutamate. By oxidative deamination through glutamate DH, ammonia is removed NADPH is produced and alpha KG forms which can enter CAC.

54
Q

Tryptophan is precursor of other important compounds like what

A

niacin, indolacetate, and serotonin

55
Q

No serotonin =

A

depressed

56
Q

Catabolism of Phenylalanine and tyrosine

A

If the phenylalanine hydroxylase enzyme is defective phenylalanine is in the urine so person has PKU.

57
Q

Alternative pathways for the catabolism of phenylalanine in patients with phenylketonuria:

A

Phenylalanine converted to alanine and phenylpyruvate which then becomes phenylacetate and phenyllactate. This is alternative pathway for phenylalanine catabolism.

58
Q

Valine and isoleucine catabolism:

A

Get converted to propionyl CoA.

59
Q

Catabolic pathways of three branched chain amino acids:

A

These have branched chains. Special aminotransferase takes away amino group to convert them to alpha ketoacids. These are branched chain ketoacids still. These 3 get converted to Acyl CoA using branched alpha keto acid DH complex. Very important enzyme. Similar mechanism to other dehydrogenase complexes(PDC, alpha KG DH complex). Uses CoA thiamine NADH lipoamide FADH2 as cofactors. Mechanism is identical. Use CoA which converts them to CoA derivatives. CO2 is taken out and NADH is produced. If this enzyme is not functioning properly then these branch chain keto acids are excreted in the urine and smell like maple syrup. If not treated, kid dies before 4 years old. Treatment: eat only sufficient amount of proteins but do not use it for energy. design a protein diet where these crazy amino acids are taken out.

60
Q

Tell me about woman in USA put behind bar:

A

Woman in usa put behind bar because kid die found milk bottle had ethylene glycol which is antifreeze compound very toxic don’t make lemonade in windshield washer can while she was in jail her husband used to visit and they did an experiment and she got pregnant the 2nd child start showing symptoms of toxicity and big story this girl is crazy and try to kill 2nd child and milk bottle taken from the jail good for her when this crazy story was being broadcasted 2 biochemists watched this programme and this news attracted their attention because where is she getting ethylene glycol in the jail they analyzed the bottle and found no ethylene glycol in child or on bottle found that methyl malonic acid was in the system and that was killing the child very irony that methyl malonic acid and ethylene glycol give same result got the data from previous analysis and proved it was completely wrong and in blood analysis it was methyl malonic acid presented case in court and patricia was honourably dismissed from this sentence and discharged child was avoided given branch chain amino acids and odd chain fatty acid because these will lead to the trouble and make sure child gets enough of the B12 because important cofactor

Metabolism (14 decks)

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