Term
| Define ketogeneic amino acids |
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Definition
Amino acid degraded to Acetyl CoA or acetoacetyl CoA
So called because they can produce ketone bodies |
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Term
| Define glucogenic amino acids |
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Definition
Amino acids degraded to Krebs intermediates
So called because their carbon skeletons may be used for glucose synthesis |
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Term
| What amino acids are ketogenic only? |
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Definition
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Term
| What amino acids are both gluconeogenic and ketogenic? |
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Definition
| Isoleucine, phenylalanine, tryptophan, tyrosine, threonine |
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Term
| What are the steps for normal catabolism of phenylalanine? |
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Definition
(Note: different because transanimation is not the first step)
1. Hydrolation to form tyrosine
2. Transamination of tyrosine
3. Catabolism of α-keto acid of tyrosine |
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Term
| What enzyme catalyzes the conversion of phenylalanine to tyrosine? |
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Definition
| Phenylalanine hydroxylase |
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Term
| What are additional reactants/cofactors needed for the conversion of phenylalanine to tyrosine? |
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Definition
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Term
| What enzyme regenerates BH4 from BH2 by use of NADH? |
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Definition
| Dihydrobiopterin reductase |
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Term
| What are the affected genes/enzymes in PKU? |
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Definition
Phenylalanine hydroxylase gene (99% cases)
Dihydrobiopterin reductase (1% cases) |
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Term
| What are symptoms of untreated PKU? |
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Definition
| Mental retardation, CNS damage, hypopigmentation |
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Term
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Definition
Blood phenylalanine levels: normally 50µM but in PKU 1000µM
Should be diagnosed within 2 days of birth |
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Term
| What is the treatment for PKU |
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Definition
| A very restricted diet with the goal to have enough Phenylalanine to survive but not too much |
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Term
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Definition
| When a pregnant woman has PKU and has to carefully restrict her diet before and during pregnancy to prevent fetal retardation |
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Term
| What happens to Phe in people with PKU? |
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Definition
It is converted to Phenylpyruvate, then Phenyllacetate and Phenyllactate.
No clear explanation for why these products cause retardation. |
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Term
| What products are low in people with PKU? |
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Definition
| Tyrosine, and all products of Tyrosine (proteins, melanin, catecholamines, fumarate) |
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Term
| What are the steps in normal catabolism of branched amino acid chains? |
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Definition
1. Transamination
2. Decarboxylation of α-keto acid products |
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Term
| What are the three branched-chain amino aicds? |
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Definition
| Isoleucine, Leucine, Valine |
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Term
| What enzyme decarboxylates the α-keto acids of branched-chain amino acids? |
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Definition
Branched-chain α-keto acid dehydrogenase (BCKAD)
(inhibited by Maple syrup urine disease) |
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Term
| What are symptoms of Maple Syrup Urine Disease? |
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Definition
Onset at 4-7 days of age, possible coma and death.
Branched chain and α-keto acids in plasma and urine.
One of these α-keto acids smells like maple syrup. |
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Term
| How is Maple Syrup Urine disease treated? |
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Definition
| Restricted intake of branched chain amino acids |
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Term
| Define the α-ketoglutarate family of non-essential amino acids and the basic reaction |
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Definition
| α-ketoglutarate → glutamate → glutamine, proline, arginine |
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Term
| What enzyme catalyzes α-ketoglutarate → glutamate by reductive amination |
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Definition
| Glutamate dehydrogenase (with use of NADH, H+, and NH4+) |
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Term
| What enzyme catalyzes glutamate → glutamine? What enzyme does the reverse reaction? |
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Definition
Glutamine synthase (requires ATP and NH4+)
Glutaminase for the reverse reaction |
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Term
| Define the oxaloacetate family of non-essential amino acids and the basic reaction |
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Definition
| oxaloacetate → aspartate → asparagine |
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Term
| Define the pyruvate family of non-essential amino acids and the basic reaction |
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Definition
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Term
| How is alanine formed from pyruvate and glutamate? |
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Definition
By transamination
Catalyzed by an aminotransferase, also produces α-ketoglutarate |
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Term
| Define the 3-phosphoglycerate family of non-essential amino acids and the basic reaction |
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Definition
3-phosphoglycerate → serine → glycine/cysteine
Methionine is also needed to form cysteine |
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Term
| What are the three steps to form Serine from 3-phosphoglycerate? |
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Definition
3-phosphoglycerate → (oxidized)
3-phosphohydroxypyruvate →(phosphoserine aminotransferase)
3-phosphoserine →
serine |
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Term
| What is needed for 3-phosphohydroxypyruvate to transform into 3-phosphoserine? |
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Definition
| Phosphoserine aminotransferase, and glutamate to give an NH4 |
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Term
| How is biosynthesis of serine regulated? |
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Definition
| Serine inhibits the first enzyme in the pathway in feedback regulation |
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Term
| Define Tetrahydrofolate (FH4) |
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Definition
| A versatile carrier of one-carbon fragments at various levels of oxidation |
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Term
| How does the body produce Tetrahydrofolate (FH4)? |
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Definition
| By intake of dietary folic acid |
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Term
| What are the three units of Tetrahydrofolate (FH4)? |
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Definition
1. A pteridine derivative
2. P-aminobenzoic acid
3. Glutamic acid
The 1-C fragments are carried on nitrogens between the pieces |
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Term
| Give two examples of reactions that require Tetrahydrofolate (FH4) |
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Definition
Synthesis of glycine from serine (takes carbon),
synthesis of methionine from homocysteine (donates carbon) |
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Term
| Why is methionine needed in the body? |
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Definition
| It is used to form 5-Adenosylmethionine (adoMet), used in many methylation reactions |
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Term
| What enzyme catalyzes the formation of adoMet from Methionine? |
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Definition
| Methionine adenosyl transferase (requires ATP) |
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Term
| After adoMet is "used up" after it transfers its methyl group, how is it regenerated? |
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Definition
The S-adenylsylhomocysteine is hydrolyzed to homocysteine and adenosine
Methionine synthase forms methionine from homocysteine (and FH4)
Methionine adenosyl transferase converts methionine and ATP to adoMet, releasing 2 Pi |
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Term
| List examples of molecules that can be formed from amino acids |
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Definition
Phospholipids, purines, pyrimidines, neurotransmitters, hormones, porphyrins, proteins
(nitrogen containing compounds) |
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Term
| What is tyrosine an important precursor of? |
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Definition
| The catecholamines, thyroid hormone, and melanin |
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Term
| What is tyrptophan an important precursor of? |
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Definition
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Term
| What is glutamic acid an important precursor of? |
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Definition
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Term
| Describe the pathway by which Tyrosine converts to Epinephrine |
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Definition
Tyrosine → (hydrolyation using BH4)
L-Dopa →
Dopamine →
Norepinphrine → (methylation using adoMet)
Epinephrine |
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Term
| Describe the pathway by which tryptophan forms serotonin |
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Definition
Tryptophan → (hydrolyation using BH4)
S-Hydroxytryptophan → (decarboxylation using PLP)
Serotonin |
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Term
| Describe the reaction by which Glutamate forms GABA |
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Definition
Glutamate → (decarboxylation using PLP)
GABA |
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