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Biochemistry > Amino Acid Metabolism > Flashcards

Amino Acid Metabolism Flashcards

1
Q

Name the essential amino acids

A

Phenylalanine, Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine (only kids), Leucine, Lysine (PriVaTe TIM HALL)

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2
Q

What do most transaminases require?

A

alpha ketoglutarate and glutamate

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3
Q

What does the direction of the reaction depend on?

A

The concentrations of the reactants because Keq~1

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4
Q

Transaminases require what as a prosthetic group

A

pyridoxal phosphate derived from vit B6

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5
Q

Which amino acids are not substrates for reversible transamination?

A

Lysine and Threonine

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6
Q

Is there a storage form of amino acids?

A

No

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7
Q

Amino acid metabolism heavily dependent on coenzymes derived from what?

A

vit B6, folic acid, B12, biotin, and niacin

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8
Q

What are Glycogenic Amino Acids?

A

amino acids whose carbon skeletons can be converted to glucose

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9
Q

What are ketogenic amino acids?

A

carbon skeletons can not be converted into glucose, but can be converted into ketone bodies (acetoacetate or acetoacetyl CoA) or acetyl CoA

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10
Q

What is the most important glycogenic amino acid?

A

Alanine

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11
Q

What are the reactions of alanine?

A 
Transamination with pyruvate (other than in protein synthesis)
Alanine Transaminase (ALT)
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12
Q

What are the reactions of Aspartate?

A 
Transamination with oxaloacetate
Aspartate Transaminase (AST)
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13
Q

Where does oxaloacetate come from?

A

intermediate from the TCA cycle

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14
Q

What are the reactions of Asparagine?

A

Synthesized from aspartate using glutamine as the amine donor (Asparagine synthase)
Catabolized to aspartate by asparaginase

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15
Q

What are the branched chain amino acids?

A

Valine, Leucine, and Isoleucine

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16
Q

What are the two common steps of branched chain amino acids?

A

Step 1: branched chain amino acid transaminase,
products=branched chain alphaketo acids
Step 2: branched chain alpha keto dehydrogenase
–>intramitochondrial enzyme

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17
Q

What does branched chain alpha keto dehydrogenase require? What are they derived from?

A

TPP, Lipoic acid, FAD, NAD, and CoASH

Thiamine, lipoid acid, riboflavin, niacin, and pentathenic acid respectively

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18
Q

What are the products from valine?

A

Propionyl CoA

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19
Q

What are the products from Leucine?

A

Acetoacetate and Acetyl CoA

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20
Q

What are the products of isoleucine?

A

Propionyl CoA and Acetyl CoA

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21
Q

What does Propionyl CoA carboxylase require?

A

Biotin

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22
Q

What does Methylmalonyl CoA mutase require?

A

Vit B12

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23
Q

What is Propionyl CoA metabolized to?

A

Succinyl CoA

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24
Q

What are two important enzymes required in the Propionyl CoA pathway?

A

Propionyl CoA carboxylase and Methylmalonyl CoA mutase

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25
What are the hydroxy amino acids?
Serine and Threonine
26
Describe how Serine is synthesized.
3-phosphoglycerate->oxidize hydroxyl group=alphaketoacid-> transaminase=serine + phosphate-> phosphatase=serine
27
What is serine metabolized to?
3-Phosphoglycerate by transamination, reduction, and phosphorylation by glycerinate kinase
28
How can Serine be converted to glycine?
serine hydroxymethyl transferase requires pyridoxal phosphate Tetrahydrofolate (THF) (metabolite of folic acid)
29
Describe the two pathways that threonine is catabolized by.
Serine (threonine) dehydratase=alphaketobutyrate-> alpha ketoacid dehydrogenase=propionyl CoA threonine dehydrogenase= acetyl CoA, glycine, or pyruvate
30
Glycine can be synthesized from what?
Serine and THF (serine hydroxymethyl transferase) Threonine (threonine dehydrogenase) CO2, NH4, and methylene THF (glycine synthase or glycine decarboxylase) *only AA that can be formed by all its constituents
31
Glycine can be catabolized by what?
Serine hydroxymethryl transferase = serine glycine decarboxylase or the reversible reaction to all constituents
32
What does THF do?
transfers one carbon units at various oxidation states among reactions requiring them (one carbon metabolism)
33
What are the uses of THF?
Serine, glycine, and histidine "resynthesis" of methionine from homocysteine synthesis of purines formation of the methyl group of thymine
34
What form of THF is most often used in other reactions?
N5, N10 methylene H4 Folate
35
What does glutamate dehydrogenase do?
removes the amine as ammonium ion used for urea synthesis (liver) or excretion (kidney) In tissues producing ammonium, it incorporates the ammonium into glutamate Reversible reaction
36
Net synthesis and catabolism of which amino acids share glutamate as an intermediate?
glutamine, proline, arginine, and histidine (catabolism only)
37
How is glutamate associated with the TCA cycle?
transamination into alpha ketoglutarate
38
Catabolism of arginine and proline happen through which intermediate?
glutamate gamma semialdehyde
39
Catabolism of histidine forms what?
glutamate, also involves formation of N5 formimno THF
40
Glutamine serves as a transport form of what?
ammonia transported to other tissues requiring ammonia for the synthesis of purines, pyrimidines also supplies the bulk of excreted ammonia from the kidneys
41
Which are the sulfur amino acids?
methionine and cysteine
42
What is the only reaction using N5 methyl THF?
homocysteine to methinonine requiring N5 methyl THF and vit B12
43
What is methionine converted to when not being used for protein synthesis? by what?
S-adenosylmethionine | by methionine adenosyl transferase
44
Describe how cysteine is synthesized.
homocysteine + serine-->alpha ketobutyrate, ammonia ion, and cysteine cystathinine synthase or cystathionase requiring a pyradoxal phosphate
45
What is cysteine synthesis dependent on?
availability of methionine
46
What is the major route of catabolism of cysteine
oxidation by cysteine dioxygenase | after transamination, non enzymatic desulfurylation results in pyruvate and sulfite
47
What is the major route of catabolism of cysteine
oxidation by cysteine dioxygenase | after transamination, non enzymatic desulfurylation results in pyruvate and sulfite
48
Phenylalanine converted to tyrosine by what?
phenylalanine hydroxylase requiring tetrahydrobiopterin as a cofactor
49
Why is tetrahydrobiopterin important?
No vitamin precursor | cofactor for phenylalanine hydroxylase converting phenylalanine into tyrosine
50
What are phenylalanine and tyrosine catabolized to and through what?
fumarate and acetoacetate by tyrosine aminotransferase (TAT)
51
How is TAT induced?
tyrosine aminotransferase | by high concentrations of tyrosine and glucocorticoid hormones
52
How is TAT induced?
tyrosine aminotransferase | by high concentrations of tyrosine and glucocorticoid hormones
53
What is the first enzyme of the tryptophan pathway and how is it induced?
tryptophan oxygenase | induced by high concentrations of tryptophan and glucocorticoid hormones
54
What does tryptophan form during catabolism?
alanine quinolinic acid (used for synthesis of NAD in the liver) acetyl CoA
55
What is the initial step in the Lysine pathway? and what does it produce?
removal of the epsilon amino group | producing acetoacetyl CoA
56
Phenylketonuria (PKU)
group of disorders, deficiency of phenylalanine hydroxylase, small percentage are deficient in tetrohydrobiopterin metabolism phenylpyruvate excreted in large quantities toxic to CNS, IQ of 50 controlled diet low in phenylalanine supplement tetrathydrobiopterin female prego still need to restrict diet bc can get to fetus
57
Tyrosinemia type 2 (oculocutaneous tyrosinemia)
``` deficiency of tyrosine amino transferase corneal opacity (tyrosine crystals in cornea), skin lesions, variable mental retardation control diet low in tyrosine and phenylalanine ```
58
Neonatal tyrosinemia
maturitional delay in activity of p-hydroxyphenylpyruvate oxidase usually benign and resolves in one month
59
Alcaptonuria
deficiency of homogentisate oxidase homogentisate excreted in urine, exposed to O2 turns black benign, greater probability of arthritis later in life
60
Tyrosinemia Type 1 (hepatorenal tyrosinemia)
deficiency of fumarylactoacetate hydrolase liver failure, hepatocellular carcinoma tubular dysfunction, renal failure painful neurologic crises porphyria-like sx may develop due to succinylacetone accumulate inhibiting heme synthesis NTBC or transplant
61
Maple Syrup Urine Disease (MSUD)
branched chain alpha ketoacid dehydrogenase deficiency excretory products produce maple syrup odor severe mental retardation, shortened lifespan treatment dietary

Biochemistry (3 decks)

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