Set 6 Amino Acid Catabolism

Front 1

How doe Extrahepatic Tissues remove their nitrogen?

Back 1

All of the Nitrogen is collected on Glutamate

Front 2

What Enzyme is responsible for transferring amino acids on glutamate, and what does this enzyme produce on top of Glutamate?

Back 2

Amino Transferases, and Alpha-Ketoacids get produced.

Front 3

Why do Amino groups need to be transferred to the liver before they can be eliminated from the body?

Back 3

Because free ammonia is toxic. Most use GLUTAMINE to transfer ammonia to the liver? The liver is the site of the UREA cycle

Front 4

Where does the urea cycle occur?

Back 4

In the liver

Front 5

What is the intermediate that the Amino group gets transferred to, to form glutamine?

Back 5

Gamma Glutamyl Phosphate.

Front 6

What Enzyme catalyzes the formation of gamma glutamyl phosphate, and subsequently glutamine from glutamate? How many ATP equivalents does this use?

Back 6

Glutamine Synthase. Requires 1 ATP equivalent.

Front 7

Write out the 2 step equation of producing Glutamine from Glutamate.

Back 7

Glutamate + ATP --> Gamma-Glutamyl Phosphate + ADP

Gamma Glutamyl Phosphate + NH4+ ---> Glutamine + Pi

Front 8

Where is glutamine formed prior to the Urea cycle?

Back 8

In non hepatic cells

Front 9

Why is it better to have glutamine travel in the blood to the liver rather than Glutamate.

Back 9

Because glutamate is acidic, and will therefore change the pH of the blood. Glutamine on the other hand will not change the pH of the blood.

Front 10

Once Glutamine arrives in the liver, which enzyme converts it into Ammonium + Glutamate + H20 . Once happens to Ammonium and glutamate respectively?

Back 10

Glutaminase. Ammonium will enter the Urea cycle, and Glutamate will undergo oxidative deamination.

Front 11

Which enzyme takes of the delta Amino group off of Glutamine ?

Back 11

Glutaminase

Front 12

Which enzyme takes off the alpha amino group from an Amino Acid?

Back 12

Amino Dehydrogenase.

Front 13

What is the nitrogenous excretory product of bony Fish, and what is their classification?

Back 13

Ammonia . Ammonetelic.

Front 14

What is the nitrogenous excretory product in Reptiles, and what do they conserve in the process? what is their classification?

Back 14

Uric Acid. Uricotelic. Conserves a lot of water.

Front 15

What is the nitrogenous excretory product in mammals, and what their our classification

Back 15

urea. Ureotelic.

Front 16

Which AA must all amino acids be converted to prior to entering the MT matrix for oxidative Deamination? And what type of enzyme catalyzes this reaction?

Back 16

Glutamate. Aminotransferase.

Front 17

How many enzymatic Steps does the Urea cycle have?

Back 17

4

Front 18

how many enzymatic steps does it take to produce UREA from NH4+

Back 18

5 (Urea cycle + 1 preliminary step (the creation of Carbomyl Phosphate)

Front 19

What is the process called of removing the Alpha Amino group from Glutamate, and how does it it fit into the Urea cycle?

Back 19

Oxidative Deamination. It is one of the preliminary steps to the urea cycle.

Front 20

What are the reactants and products of Oxidative deamination, and which Enzyme catalyzes this reaction.

Back 20

Glutamate dehydrogenase catalyzes Ox. Deamination.

Glutamate + H20 + NADP+/NAD+ --> Alpha-Ketoglutarate + NH4+ + NADPH/NADH

Front 21

Why is Glutamate dehydrogenase a unique enzyme with respect to its substrates.

Back 21

It can use either NADH or NADPH. Assume this process always produces 2.5 ATP>.

Front 22

How is Glutamate DHase regulated?

Back 22

It is regulated at an allosteric site by ADP/GDP and ATP/GTP. Glutamate Dhase is Positively regulated by ADP/GDP and negatively regulated by ATP/GTP.

Front 23

Does glutamate dehydrogenase catalyze a reversible reaction?

Back 23

yes!

Front 24

Where else do we see Alpha- KG in the cell

Back 24

it is a TCA cycle intermediate.

Front 25

Why is Glu DHase allosterically regulated by ATP, ADP, and their equivalents?

Back 25

Because Alpha - KG is an int cycle intermediate with the potential to make 7.5 ATP. if ADP concentration is low in the cell, Alpha KG can be made to feed into the Kreb cycle, and Glu DHase also produces an NADH equivalent, which can be used to make 2.5 ATP.

Front 26

How much ATP can be produced from A-KG entering the Kreb cycle

Back 26

7.5 ATP.

Front 27

What happens to the Ammonium group that gets removed from glutamate in the reaction catalyzed by Glutamate DHase

Back 27

It combines with HCO3- to produce Carbamoyl Phosphate

Front 28

What is the rate limiting step (RLS) of the Urea cycle?

Back 28

The production of Carbamoyl Phosphate from HCO3- + 2 ATP +NH4+ .

Very similar to "activating" Acetyl CoA to malonyl CoA. A good leaving Group (PO4) is added.

Front 29

what enzyme catalyzes the production of Carbomoyl Phosphate

Back 29

Carbomoyl phosphate Synthetase 1 (CPS I)

Front 30

What is the balanced reaction for the production of Carbamoyl Phosphate? How any ATP equivalents are used?

Back 30

NH4+ + HCO3- + 2 ATP --> Carbamoyl-Phosphate + 2ADP + Pi

Front 31

Where does the Bicarbonate ion (HCO3-) come from?

Back 31

Readily available in the mitochon as it is a waste product from Cellular resp.

Front 32

What is the reaction for the first step of the Urea Cycle? and what enzyme catalyzes this reaction?

Back 32

Carbamoyl Phosphate + Ornithine --> Citrulline + Phosphate.

Ornithine Transcarbamoylase.

(note, Ornithine retains its structure throughout the whole cycle, groups just get added to it. think 99 B line lol)

Front 33

Can ornithine and Citrulline be considered Amino acids?

Back 33

Yes. Have "N, C alpha, C-oh", but aren't used to build up proteins.

Front 34

WHat molecule is Ornithine Analogous in the TCA cycle?

Back 34

Oxaloacetate (OAA)

Front 35

Where does the first step of the Urea Cycle occur within the cell? (i.e. where is the enzyme located, and what is its name? )

Back 35

Ornithine transcarbamoylase. This reaction occurs in the Mitochondrial MATRIX. Only step in the Urea cycle that occurs in the matrix.

Front 36

What enzyme catalyzes reaction 2 of the urea cycle. and what are the Reactants, products, and the intermediate? Where does this rxn occur in the cell?

Back 36

Argininosuccinate Synthetase. (AsS). Aspartate + ATP + Citrulline --> Argininosuccinate + AMP + PPi

intermediate- Citrulyll-Amp

In the Cytosol.

Front 37

How many ATP equivalents are used to synthesize Argininosuccinate from Citrulline

Back 37

2 atp equivs, 1 ATP Molecule.

Front 38

Why is Amp added to Citrulline?

Back 38

It is a good leaving group when adding on aspartate

Front 39

AsS is consuming Aspartate to make Argininosuccinate. How is the Aspartate replenished?

Back 39

Glutamate + OAA ---> Alpha -KG + Aspartate.

Aminotransferase catalyzed reaction

Front 40

how does the OAA used in replenishing the Aspartate get replenished in the cell?

Back 40

Fumarate is produced during the third step of the urea cycle, and the fumarate will enter the Kreb cycle to reform Oxaloacetate.

Front 41

Describe step three of the Urea Cycle

Back 41

Arginino succinate undergoes cleavage to form Fumarate and Arginine. This reaction is catalyzed by Argininosuccinase in the cytosol . THis reaction is reversible.

Front 42

Which is the only reversible step in the UREA cycle?

Back 42

The third step, the cleavage by argininosuccinase to produce arginine + Fumarate.

Front 43

how many ATP equips are used in the Urea Cycle (including the preliminary reaction). How do we get a "pay off" from the Urea cycle?

Back 43

4 equivalents (2 to male carbamoyl phosphate, and 2 to argininosuccinate)

Fumarate is produced, and can enter the Kreb cycle. This produces 1 NADH (2.5 ATP)

(Just speculation, but I think we can also get Energy from Alpha-KG (7.5 ATP), as well as the 2.5 ATP gained from making NADH/NADPH with Glu Dhase)

Front 44

What are the reactants, the products, and the enzyme used in the fourth step of the Urea cycle?

Back 44

Arginase catalyzes the Hydrolytic cleavage of Arginine into Urea and Ornithine. This occurs in the Cytoplasm, however Ornithine must get transported back into the matrix to keep the cycle going).

Net rxn: H2O + Arginine --> Ornithine + Urea.

Front 45

Where do the nitrogens on Urea come from, and where does the carbon come from?

Back 45

One Nitrogen comes from the N from Carbamoyl Phosphate (which came from Ammonium (which used to be glutamate)), and the other Nitrogen came from Aspartate. The carbon came from the Carbamoyl Carbon (which came from HCO3-)

Front 46

How does Fumarate (from step 3) get into the Mitochondrial Matrix?

Back 46

There is no transporter for fumarate to get into the MT matrix, so it must be converted into malate first. Malate gets into the MT matrix through anti port, using Alpha-KG, which goes into the cytosol.

Front 47

Fumarate to Malate occurs in the Matrix of the MT during TCA cycle, how does it occur in the cytoplasm when converting Fumarate to malate to get it into the MT matrix?

Back 47

There is an isozyme (of Fumarate Hydratase) that performs the same catalysis as the equivalent in the matrix of the mitochondria.

Front 48

How much Energy is produced by getting Fumarate (from Step 3) back into the Kreb Cycle

Back 48

2.5 Atp (from 1 NADH). This offsets the cost of the UREa Cycle