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NA > L15: Amino Acid & Urea Metabolism > Flashcards

L15: Amino Acid & Urea Metabolism Flashcards

1
Q

Deamination

What does an amino acid that has been transaminated or deaminated turn into?

A

Their alpha-keto forms

Happens by replacing amino group with a carbonyl

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2
Q

Deamination

What is the universal acceptor of amino group?

A

alpha-ketoglutarate, which accepts amino groups/nitrogen in the liver to form glutamate

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3
Q

Deamination

Why must we get rid of the amino group?

A

Neither TCA nor beta-oxidation processes have a way to deal with them!
- We can only process carbons + hydrogens with these catabolic processes

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4
Q

Deamination

What is the first step in deamination?
Where does this step occur?
Is it reversable?

A

Transamination

In the liver

Yes, it is reversable

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5
Q

Deamination

What is the mechanism behind transamination?

Reactants
Enzyme
Cofactor - what does it hold?
Products

A

1) Alpha keto acid accepts amino groups from AA
2) AA becomes alpha-ketoacid
3) Alpha-ketogluterate becomes glutamate

Reactant: Amino Acid + alpha keto acid
Enzyme: Aminotransferases
Cofactor: PLP = temporary amonia holder
Product: Amino acid + alpha keto acid

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6
Q

Deamination

What holds the amonia?

A

L-glutamine

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7
Q

Deamination

Post transamination, what is the goal?

A

To get ammonia to the liver

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8
Q

Deamination

What are the two methods though which ammonia is transported to the liver?

A

Glutamine or Alanine

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9
Q

Deamination

Describe the problem with Glutamate and the liver

A

Glutamate can be an acceptor molecule in the liver

But can not pass though the membranes whilst carrying ammonia as it is toxic

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10
Q

Deamination

How is glutamine used as a transporter in the liver?

What is the enzymes used during this pathway?

A

1) Activation of glutamate using ATP
glutamine synthetase

2) Addition of the second equivalent of ammonia to make Gln
glutamine synthetase

Glutaminase chops off ammonia in liver to remake glutamate
glutaminase

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11
Q

Deamination

How is alanine used as a transporter in the liver?

What is the enzymes used during this pathway?

A

Pyruvate is in high abundance in exercising tissues.

The liver is able to conduct gluconeo, which “packages” pyruvate back into glucose to feed back to the hungry muscles

Net result:
1) Pyruvate + Glutamate -> Alanine
2) Alanine is transferred to the liver
3) In liver Alanine regenerates pyruvate and turns it into glucose

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12
Q

Excretory Forms

What are the 3 Major Excretory Forms of nitrogen?

A

1) Ammonia
2) Urea
3) Uric Acid

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13
Q

Excretory Forms

What are the traits of Ammonia?

A
  • Alkaline (accumulation raises pH)
  • Uses mainly by aquatic animals
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14
Q

Excretory Forms

What are the traits of Urea?

A
  • Neutral
  • High water loss when excreted
  • Many vertebrates
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15
Q

Excretory Forms

What are the traits of Uric Acid?

A
  • Insoluble
  • Excrete w/o lots of water loss
  • Birds, reptiles
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16
Q

Ammonia in the liver

How does Ammonia enter the urea cycle?

A

Via Carbamoyl phosphate

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17
Q

Ammonia in the liver/ Pre-Urea Cycle

How is Carbamoyl Phosphate formed?

What enzyme catalizes the reaction?

A

1) Activate bicarbonate with ATP
2) Displace phosphate with amino group
3) Activate resulting carbmate with ATP

Enzyme: Carbamoyl Phosphate Synthase 1

18
Q

Urea Cycle

What are the 4 steps of the urea cycle?

A
19
Q

Urea Cycle

Describe the link between the Urea and TCA cycle

A

The fumarate that leaves the urea cycle become malate

Malate then enters TCA cycle

20
Q

Urea Cycle Regulation

What are the two key components in Urea Cycle Regulation?

A
  • Arginine increases the production of N-Acetylglutamate
  • A lot of arginine = a lot of urea cycle intermediates
  • The commitment step, is promoted by N-Acetylglutamate
  • N-Acetylglutamate is a signal molecule for a high concentration of both acetyl-CoA (energy) and glutamate (ammonia)
21
Q

AA Catabolism

What are the 5 cofactors in amino acid catabolism

A

PLP
Biotin
THF
AdoMet
THB

22
Q

AA Catabolism

Where is PLP active?

A

Transamination

23
Q

AA Catabolism

Where is Biotin active?

A

One-carbon transfer (CO2)

24
Q

AA Catabolism

Where is THF active?

A

One-carbon transfer (intermediate oxidation states)

25
Q

AA Catabolism

Where is AdoMet active?

A

one-carbon transfer (CH3)

26
Q

AA Catabolism

Where is THB active?

A

Oxidation/reduction

27
Q

Breakdown of deaminated carbon skeletons

What does ketogenic AA tun into?

A

Ketone bodies

28
Q

Breakdown of deaminated carbon skeletons

What are ketone bodies broken down into?

A

Can be broken down to make glucose

29
Q

Breakdown of deaminated carbon skeletons

What can Gluconeogenic AA be broken down into?

A

Glucose

30
Q

CATABOLIC PATHWAY FOR TRP/ALA/SER/CYS AND THR/GLY

What do Trp, Ala, Ser, Cys, Thr and Gly break down into?

A

Ultimate end goal for all six of these AA = make pyruvate

  • Ser/Ala/Trp/Cys → Pyruvate
  • Thr/Gly → Ser
31
Q

CATABOLIC PATHWAY FOR PHE AND TYR

What does the pathway involve?

What are Phe and Tyr broken into?

A
  • Breakdown involves oxygen
  • Defects of enzymes → PKU and
    Tyrosinemia

Products
- fumarate (gluconeogenic)
- acetoacetyl-CoA (ketogenic)

32
Q

CATABOLIC PATHWAY FOR VAL/ILE/LEU

What do Val, Ile, and Leu break down into?

A
  • Val & Ile -> succinyl-CoA
  • Ile -> acetyl - CoA
  • Leu -> acetyle - CoA
33
Q

CATABOLIC PATHWAY FOR ASP AND ASN

What are Asp and Asn broken into?

A

Oxaloacetate

34
Q

AMINO ACID BIOSYNTHESIS

What are amino acids incorporated though?

A

glutamate and glutamine

35
Q

AMINO ACID BIOSYNTHESIS

How is glutamine synthesized?
Pathway?

A
36
Q

AMINO ACID BIOSYNTHESIS

What is the Glutamine Amido transferase pathway?

A
37
Q

AMINO ACID BIOSYNTHESIS

How many AAs can mammals synthesize?

A

Can only synthesize about half of the AAs

38
Q

THE NITROGEN CYCLE

What is Nitrification?

A

Oxidation of NH3 to NO3-

39
Q

THE NITROGEN CYCLE

What is denitrification?

A

Aerobic reduction of NO3- to N2

40
Q
A

NA (6 decks)

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