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51 Cards in this Set

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What are the 3 reactions of amino acid nitrogen?
a) Transamination: tansfer between ∂-amino acid and a ∂-Keto acid…
b) removal of amino acid ∂-amino group…
c) reactions with an amino side chain carboxamide group
(a) What is required for tansamination reactions?
(b) Is energy required, why or why not?
(a) Aminotransferase and PLP…
(b) no energy since, the Km is at about 1… shift in accordance with concentration
1. Match the following with their cognate amino acids: pyruvate, oxaloacetate, ∂-KG

2. From which vitamin is PLP derived?

3. What part of PLP is active and what to functions does it serve? (
1. pyruvate-alanine, oxaloacetate-aspartate, ∂-KG-glutamate

2. B6

3. The aldehyde, a) allows the cofactor to covalently bind to the enzyme, and b) allows the cofactor to hold on to the amino acid (known as a SCHIFF BASE when the PLP is bound up)
None
In a transaminase rxn:

1. On a keto acid what does a carbonyl become? (note this rxn also happens in reverse)

2. On the amino acid, what does the ∂-amino acid and ∂-hydrogen become?
1. ∂-amino and ∂-hydrogen

2. carbonyl
None
1. How many ATPs are required in a tranaminase rxn?

2. what drive the reaction in one way or the other?
zero... no energy is required... Km = zero... there is a keto acid and an amino acid on each side of the equation

2. le Chatlier
What part of PLP is active and what does it do?
Aldehyde, it allows the co-factor (PLP) to hold the amine group and the enzyme during the rxn.
What types of enzymatic rxns does the cofactor PLP participate in?
transamination, decarboxylation, ß-elimination, gamma-elimination, and racemization
1. At pH 7.3, what is the ratio of NH4 to NH3?

2. which form is more permeable to the cell membrane, ammonium (NH4+) or ammonia (NH3)?
1. 100 to 1

2. ammonia (NH3)
None
What type of reaction does glutamate dehydrogenase participate in?
oxidative deaminization (removal of an amino acid ∂-amino group) , where glutamate loses it's amine group to become ∂-KG
Give the pathway for the glutamate dehydrogenase reaction? (hint: 2-steps)
glutamate + NAD --> imino (=N2) + NAD(P)H --> ∂-KG (note: a water molecule attacks the imino group)
None
Thus, glutamate dehydrogenase rxn, if glutamate is oxidized, what is reduced?
NAD+, which is reduce to form NADH, and frees ammonium
(a) When will the glutamate rxn be more likely to occur, during high energy demand or low energy demand (b) Why
(a) High energy demand, thus [ADP or GDP] is high.

(b) this makes sense when you consider in low [ATP or GTP] you would want more ∂-KG, which is a TCA cycle intermediate that will yield NADH from NAD
(a) What type of rxn does L-amino acid oxidase participate in?

(b) and where does this rxn occur? (Hint: we recieve L-amino acids and they must be broken down... where in the cell would you do this?
(a) oxidative deamination (removal of an amino acid ∂-amino group)…

(b)peroxisomes
What must follow a L-amino acid oxidase rxn?
catalase, where H202 (a reactive molecule) is converted to water and oxygen
Which amino acid does D-amino acid oxidase participate in?
ONLY Glycine
(a) What type of reaction does serine/threonine dehydratase participate in?

(b) what cofactor is required?

(c) What leaving group is formed as an intermediate in this rxn?
(a) direct dehydrogenation/ deamination by dehydratase (removal of an amino acid ∂-amino group),

(b) PLP,

(c) an imine group, which can be hydrolyzed by water to form a carbonyl
1. What is the relationship between the Glycine cleavage system and teh Glycine Synthetase rxns?

2. What is the the product of Serine and Threonine in the serine/threonine dehydratase rxn?

3. In the Serine/Threonine dehydratase rxns, what cofactor is required?
1. They are forward and reverse rxns actions, where glycine synthetase forms glycine and THF, and glycine cleavage forms Methylene-THF (to form a 1-C unit)

2. serine --> pyruvate + NH4… and threonine --> ∂-Ketobutyrate + NH4

3. PLP
None
REVIEW TRANSCRIPT LECTURE 2: PAGE 45: GLYCINE SYNTHASE
1. Name the four types of rxns involved in the removal of the ∂-amino group + the important rxns in these goups.

2. Which of these rxns does not require water?
1) Oxidative deamination…
a) Glutamate dehydrogenase
b) L-Amino acid oxidase
c) D-Amino acid oxidase (for glycine)

2) direct dehydration/deamination by dehyratase…
a) serine/threonine dehydratase

3) cleavage of glycine…
a) glycine cleavage system

4) direct deamination
a) histamine ammonia lyase (histidase) NO WATER REQUIRED
Which deamination rxn is reversible
oxidative deamination rxns
a) Name one example of direct deamination.

b) What is meant by direct deamination?

c) what is the product of the histidine ammonia lyase (histidase) rxn?
a) histadine ammonia lyase (histadase)…

b) there is no hydration (does not require water), instead there is a formation of a C=C…

c) Urocanate + NH4
1. Name the 3 main classes of reactions involving amino acid nitrogen.

2. Name the 4 reactions of the Amino Acid Side Chain Carboxamide group rxns.
a) Transamination,

b) removal of the amino acid nitrogen,

c) reactions with an amino acid SIDE CHAIN CARBOXAMIDE group

2.

Deamidation:
a) Glutaminase
b) Asparaginase

Amidation:
c) glutamine synthetase
d) asparagine synthetase
a) What happens in side chain reactions involving Asp and Glu.

b) Name the enzymes involved in these rxns.

c) What is the general role of a synthetase?
(a) amide group is added or subtracted from the Carboxamide Group

(b) Glu/Gln or Asp/Asn

c) A synthetase uses an ATP to add an a nitrogen to an amino acid
(a) For rxns involving the side chain carboxamide group, which requires energy the addition or subtraction of the amide?

(b) And in what form?
a) addition, ATP…
1. How does ATP facilitate the addition of Nitrogen?

2. Where does the the nitrogen come from for the Asp/Asn and the Glu/Gln rxns?

3. Why is the glutamine synthetase rxn important?
1. ATP is a better leaving group than a hydroxide.

2. . Asp/Asn comes from glutamine and Glu/Gln comes form NH4

3. Glutamine is an important carrier of nitrogen in the body
None
(a) What key role in the urinary system do Asparaginase and Glutaminase play?

(b) Why does this make sense?
(a) urinary pH…

(b) the release of NH4 can help raise the pH
What effect will glutamine synthetase have on urinary pH?
Since it will add an NH4 to glutamate, it will lower the pH.
In the addition of an amide to glutamate, where ATP is required along with NH4, what does the ATP do?
The phosphate on the intermediate is a good leaving group that is needed to form the carboxamide (O=C-NH2)
What is an important carrier of nitrogen in the body and serves as a nitrogen donor in biosynthetic rxns?
Glutamine
Which cells actively eliminate ammonia from the body?
liver hepatocytes
1. What role does glutamate dehydrogenase play?
1. it can grab the nitrogen from an amino acid and transfer it to ∂-KG ... forming glutamate and liberating NH4 for elimination in the urea cycle (in the mitochondria)
None
What other rxn, besides the glutamate dehydrogenase rxn, can glutamate take part in that is in important in the the urea cycle?
Where the nitrogen in Glutamate will transfer its nitrogen to Oxaloacetate forming --> aspartate (which plugs into the urea cycle - in the cytosol)
None
Describe (draw) the urea cycle.
a) Which step regulates the urea cycle? (it is the slow step)

b) what is required in this step?
a) carbamoyul phosphate synthetase I reaction (CPSI)…

b) 2 ATP
What is the handle where nitrogens will be placed in the the urea cycle?
ornithine
How many ATP and high energy phospate bonds are used in the urea cycle?
3 ATP and 4 phosphates
What is the primary site for the urea cycle?
liver (mitochondria and cytosol)
Which Mn2+ dependent rxn restore the "handle", ornithine in the urea cycle?
arginase
a) What serves as the short term (up) regulator of the urea cycle?

b) Why does this make sense?
a) High [arginine] drives the rxn of glutamate + acetyl CoA --> N-acetylglutamate… N-acetlyglutamate up regulates the slow step (CPSI)…

b) glutamate is going to go to ∂-KG which will liberate NH4 that is being plugged into the urea cycle... but more important as excess AA are transaminasing ∂KG to Glutamate this will result in high Glutamate to react with acetyl CoA.
How is long term regulation of the urea cycle accomplished?
gene induction
Why is urea not recaptured in the kidneys?
no urea receptors
How does fumarate intermediate link the urea cycle and the TCA cycle?
fumarate is formed by the conversion of arginosuccinate to arginase Fumarate will enter the TCA cycle and eventually transition to oxaloacetate which be converted to aspartate and feed back into the urea cycle
What clinical manifestation would a lack of a urea cycle enzyme cause?
hyperammonemia and a low BUN.
With the exception of ornithine transcarbamylase (OTC) inherited disorders of the urea cycle, what type of inheritance are they?
OTC is X-linked, the others are autosomal recessive
What is the severity of undiagnosed urea cycle deficiencies?
usually fatal
How would one bring up ornithine levels in a clinical setting?
administer arginine
What is the function of benzoate and phenylbutryate as drugs in urea cycle deficiencies (hyperammonemia)?
phenylbutyrate uses glutamine… benzoate uses glycerine, and thus packages them for elimination… The body sense the loss of glycerine and glutamine and replaces them and in doing so eliminates NH4 from the body
Name the 3 types of oxidative deamination reactions (loss of an ∂-alpha amino group).
(1) glutamate dehydrogenase (glutamate -> ∂-KG)

(2) L-Amino Acid Oxidase (L-AA -> ∂-KA + NH3 + FMNH2)

(3) D-Amino Acid Oxidase (ONLY for glycine)
(a) Name the direct dehydration/deaminatino by dehydratase reaction (loss of an ∂-alpha amino group).

(b) what two things are needed in this type of reaction?
(a) Serine/threonine dehydratase (minor)

(b) PLP and H2O
(a) Name the cleavage of reaction (loss of an ∂-alpha amino group... Note this reaction can go in both directions depending on the net flux)

(b) What is needed in the (forward) anabolic direction?

(c) what is needed in the (reverse) catabolic direction?
(a) Glycine cleavage system/Glycine Synthase rxns

(b) Glycerine synthase + FH4-Met + NH4 + CO2

(c) FH4 + THF + NAD+
Name the direct deamination reactiaon
Histidine ammonia lyase reaction (histidase)