PHR912 SYNTHESIS & DEGRADATION OF AA

block 3 week 3

how many of the 11 nonessential-AA can be synthesized from glucose + nitrogen source?

10

What is tyrosine synthesized from?

Essential phenylalanine

Large amounts of these AA are needed in the diet:

Arginine

Phenylalanine

Methionine

These non-essential AA are produced from glucose via the intermediates of glycolytic pathway:

Ser

Gly

Cys

Ala

These non-essential AA are produced from intermediates of the TCA cycle:

Arg

Asparagine

aspartate

glutamate

glutamine

proline

Alpha-ketoglutarate is a precursor for what AA?

Glutamine

glutamate

proline

arginine

OAA is a precursor for what AA?

Asparagine (ASN)

Aspartic acid (ASP)

The fate of carbon of AA during the fasting state:

Carbon skeletons of AAs produce glucose, ketone bodies, and CO2

The fate of carbon skeletons in AA during the fed state:

Intermediates of AA metabolism are converted to glycogen and triacylglycerols (for storage in the adipose)

Only what organ contains all the pathways of AA synthesis and degradation?

Liver

Ser is generated from what?

3-Phosphoglycerate

Serine can go on to synthesize what amino acids?

Glycine

Cysteine

Alanine is produced via:

Transamination of pyruvate 

Degradation of Ser, Gly, Cys, and Ala produce what?

Regenerate pyruvate

Glycolytic/ gluconeogenic pathway intermediates

Ser, Gly, Cys, and Ala can produce:

Glucose

get fully oxidized to CO2

Serine synthesis is increased by:

Induction of 3-phosphoglycerate  dehydrogenase

Serine synthesis is decreaed by:

Feedback inhbition of phosphoserine phosphatase by serine

What two AA can serine produce?

Gly and Cys

Cys can get converted into what?

Pyruvate to make Ala

Glycine is produced from what via a reversible reaction involving what 

Serine vis tetrahydrofolate

where is FH4 derived from?

folic acid

During the formation of Cys, what provides the carbons and nitrogen?

Ser

During the formatino of Cys, what is the sulfur provided by?

Met

Since the sulfur for CYS comes from MET, if there is a MET deficiency, it can be saved by?

An adequate source of CYS

PLP is the active form of what?

vitamin B6

PLP is the only route of what?

Homocycteine degradation

A deficiency of B6 / defect in cystathionine synthase leads to:

Homocysteinemia (accumulation of homocysteine)

PAPS 

3 phosphoadenosine 5- phosphosulfate

what does PAPS do?

Sulfate donor in the degradation of cysteine

ALA is produced via:

Reversible transamination from pyruvate via alanine transaminase

Alanine is a major what amino acid?

Gluconeogenic amino acid for transport of carbon and nitrogen to the liver

Glutamate is derived from:

Alpha-ketoglutarate via transamination OR

Glutamate dehydrogenase

Alpha-ketoglutarate in the liver can form what?

Malate and via gluconeogenesis forms glucose

When histidine gets degraded by histidase, 5 of its carbons:

Ultimately form glutamate

FIGLU:

Formiimino-Glutamate

Transfer of 1 carbon of FIGLU to the tetrahydrogolate pool releases what?

NH4 and glutamate

When folate concentration is low, FIGLU is what?

Excreted in urine

Glutamine is produced from glutamate via:

Glutamine synthetase

What does glutamine synthetase do?

Add NH4 to carboxy group of side chain on glutamine, forming an amide

How does Glutamine → glutamate get catalyzed?

Glutaminase

Why is glutaminase very important in the kidney?

NH3 enters urine and decreases the acidity

What is a precursor AA for proline?

Glutamate

What is synthesized from glutamate via its semialdehyde?

Arginine

Arginine can be transaminated into:

Ornithine, a urea cycle intermediate

Urea cycle produces this amino acid:

Arginine

Arginine is not essential in adults, but is essential in:

Children

Arginine gets cleaved by what in the urea cycle to produce urea and ornithine?

Arginase

Excess ornithine in the urea cycle gets transaminated to:

Semialdehyde, oxidized to glutamate

Asp is produced via transamination of:

OAA

Asp ←> OAA is what?

Readily reversible reaction that can regenerate OAA

Asparagine is formed from what AA?

Aspartate

What enzyme catalyzes aspartate → asparagine?

Asparagine synthetase

asparagine be degraded back into what AA?

Aspartate, generating NH4

What enzyme catalyzes asparagine → aspartate?

Asparaginase

During the formation of asparagine, what provides the nitrogen for forming the amide group?

Glutamine

What statement is wrong about glutamate-5-semialdehyde?

All are correct

Which statement is wrong about arginine metabolism?

Arginine is converted to aspartate

What statement is wrong about the following rxn?

Is readily reversible

What statemetn is wong about glycine and serine catabolism?

In the GCC-catalyzed reaction, one-carbon group from glyine is donated to THF to form methyl-THF

What statement is wrong about glutamate-5-semialdehyde?

All are correct

glutamate either is converted to or is derived from each of the following EXCEPT:

Leucine

The biosynthesis of what AA involves reactions which are also part of the urea cycle?

Arginine

Which statement is wrong about alanine metabolism

None

Which statement is incorrect about the synthesis of AA?

Alanine is synthesized from serine by a one-carbon rearrangement

What statements are correct about eniluracil and dihydropyrimidine dehydrogenase (DPD)?

DPD converts 5-FU to dihydro-5-FU

Eniluracil improves the efficacy of 5-FU

Thus, the combination therapy (5-FU + eniluracil) was developed for the treatment of solid tumors

Which is an incorrect pair?

Lysine : Butyrate

The folloiwng mammalian enzymes do not catalyze reactions that produce free ammonia (or ammonium ion):

None of the above

As AAs are degraded, their carbons are converted to:

CO2

compounds that generate glucose in the liver

pyruvate and tca cycle intermediates: alpha-ketogluatate, succinyl CoA, fumarate, OAA

Ketone bodies or their precursors: Acetoacetate, acetyl CoA

Glucogenic AA:

AAs if their carbons are converted to glucose

Ketogenic AA:

If carbons are converted to acetyl CoA or acetoacetate

Non-essential AAs are: (minus TYR)

Glucogenic

Tryptophan produces ____, which produces what?

Alanine, pyruvate

Met, Thr, Val, and Ile all form what?

Succintl CoA

Phe, after conversion to ____, forms ____

TYR, fumarate

Ketogenically, what does Trp, Thr, and Ile produce?

Acetyl CoA

Phe ketogenically produces what?

acetoacetate

what are the 2 essential AA that are exclusively ketogenic?

Lys, Leu

Alanine is

glucogenic

Arginine is

Glucogenic

Asparagine is

Glucogenic

Aspartate is

Glucogenic

CYS is

Glucogenic

Glutamate is

Glucogenic

Glutamine is

Glucogenic

glycine is

glucogenic

proline is 

Glucogenic

serine is

glucogenic

tyrosine is

ketogenic and glucogenic

Histidine is

Glucogenic

Isoleucine is

glucogenic and ketogenic

leucine is

ketogenic

lysine is

ketogenic

methionine is

glucogenic

threonine

glucogenic and ketogenic

tryptophan is

ketogenic and glucogenic

valine is

glucogenic

phenylalanine is

ketogenic and glucogenic

serine is derived from ____ via ____

glucose, 3-PG

glycine and serine are: 

Interchangeable

glycine and serine require ____ for interchangability

N5,N10-methylene THF