Breakdown and Synthesis of Amino Acids Flashcards
Breakdown of serine
Serine Direct/Self Deamination
Serine Dehydratase
1) Dehydrates the OH group to form double bond
2) deaminates serine by adding H2O to produce Pyruvate and Amonnium
- Amonnium is not transferred to Alpha-Ketogluterate
Breakdown of Threonine
Threonine Direct/Self Deamination
Threonine Dehydratase
1) Dehydrates the OH group to form double bond
2) Deaminated threonine by adding H2O to product alpha-ketobutyrate and NH4+
- Ammonium is not transferred to Alpha ketogluterate
Which amino acids are broken down to Acetyl CoA and AcetoAcetyl CoA
Aliphatic Branched chains (Leucine, Isoleucine, and Lysine
Aromatic Amino Acids (Tryptophan, Tyrosine, Phenylalanine)
Breakdown of Phenylalanine
Aromatic amino acid so requires oxidases
1) Phenylalanine-> Tyrosine
- via Phenylalanine Hydroxylase (monoxygenase)
- Tetrahydrobiopterin-electron carrier; converted to quinonoid biopterin
- O2-> H2O
2) Transamination-Amino group converted to Keto group
- product p-hydroxyphenylpyruvate
3) P-hydroxyphenylpyruvate hydroxylase (dioxygenase)
- produced HOMOGentisate
4) Homogentisate Oxidase (dioxygenase)
- ring opening
4) isomerization
5) Hydrolyzed to produce FUMURATE AND ACETOACETATE-> AcetoAcetyl CoA
Breakdown of Tryptophan
Aromatic amino acid so requires Oxidases
**converted to alanine and acetoacetate via several oxidases
1) Tryptophan -> Ringopening of 5C double bond ring via dioxygnease
2) Aldehyde reduced to amino group
3) Oxygenase
- adds OH beside Amino group
4) Alanine is released
5) Dioxygenase acts upon
- 11 steps later forms acetoacetate
Glutamate Breakdown
-Demaminated into alpha ketogluterate
Glutamate Dehydrogenase
2 Step Process:
1) Glutamate is oxidized to form Schiff Base, NAD+ reduced to NADH
2)Schiff Base Intermediate which is hydrolyzed to produce a Keto group to form alpha ketogluterate and NH4+ is released
Gln breakdown
1) Glutamine-> Glutamate
- Hydrolyzed via Glutaminase
2) Glutamate-> Alpha ketogluterate
Glutamate dehydrogenase
2 Step Process:
1) Glutamate is oxidized to form Schiff Base, NAD+ reduced to NADH
2)Schiff Base Intermediate which is hydrolyzed to produce a Keto group to form alpha ketogluterate and NH4+ is released
Proline Breakdown
1) Proline is converted to Glutamic y-semialdehyde (2 steps)
2) Glutamic Y-semialdhyde is oxidized to Glutamate
3) Glutamate-> Alpha Ketogluterate
2 Step Process:
1) Glutamate is oxidized to form Schiff Base, NAD+ reduced to NADH
2) Schiff Base Intermediate which is hydrolyzed to produce a Keto group to form alpha ketogluterate and NH4+ is released
Arginine Breakdown
1) Arginine -> Ornithine + urea
- Hydroxlyzed by Arginase
- ornithine transported into matrix of mitochondria
2) Ornithine-> Glutamic y-Semialdehyde
- R group amine oxidized to Aldehyde
3) Glutamic y-semialdehyde oxidized to Glutamate
4) Glutamate-> Alpha ketogluterate
2 Step Process:
1) Glutamate is oxidized to form Schiff Base, NAD+ reduced to NADH
2) Schiff Base Intermediate which is hydrolyzed to produce a Keto group to form alpha ketogluterate and NH4+ is released
Histidine Breakdown
Multistep process with 4- imidazolone-5-proprionate intermediate
-then to glutamate-> alpha Ketogluterate
2 Step Process:
1) Glutamate is oxidized to form Schiff Base, NAD+ reduced to NADH
2) Schiff Base Intermediate which is hydrolyzed to produce a Keto group to form alpha ketogluterate and NH4+ is released
Valine Breakdown
1) Valine-> Propionyl CoA
2) Propionyl CoA -> Methylmalonyl CoA
- via Propionyl Carboxylase
- Prosthetic Group-biotin
3) Methylmalonyl CoA-> Succinyl CoA
- Methylmalonyl CoA mutase
- Vit B12 (Cobalamin)
Isoleucine Breakdown
1) Isoleucine-Propionyl CoA
2) Propionyl CoA -> Methylmalonyl CoA
- via Propionyl Carboxylase
- Prosthetic Group-biotin
3) Methylmalonyl CoA-> Succinyl CoA
- Methylmalonyl CoA mutase
- Vit B12 (Cobalamin)
Methionine Breakdown
1) Methionine + ATP-> S-Adenosyl Methionine(SAM)
2) SAM donates activated methyl group to form S-Adenyosyl Homocysteine
3) S-Adenosyl Homocystein Hydrolyzed to Homocystein
- releasing Adenosine
4) Homocysteine + Serine -> Cystathionine
- via Cystathionine Synthase
5) Cystathionine-> alpha-ketobutyrate + Cysteine
- via Cytathioninase Hydrolyzes
5) Alpha Ketobutyrate-> Propionyl CoA
6) Propionyl CoA -> Methylmalonyl CoA
- via Propionyl Carboxylase
- Prosthetic Group-biotin
7) Methylmalonyl CoA-> Succinyl CoA
- Methylmalonyl CoA mutase
- Vit B12 (Cobalamin)
Aspartate Breakdown
Direct Deamination into OAA
Aspartate-> OAA
- Aspartate Transaminase + PLP
- alpha amino group transferred to alpha ketogluterate to form Glutamate
Asn Breakdown
1) Asparagine-> Aspartate
- Asparaginase-hydrloyzes to remove NH4+ of R group
2) Asprate-> OAA
- Aspartate Transaminase + PLP
- alpha amino group transferred to alpha ketogluterate to form Glutamate
Glutamine Synthesis
Glutamine Synthetase
1) Glutamate Phosphorylated to acyl Phosphate Intermediate
2) Ammonia (NH3+) displaces the phosphate producing Glutamine
Aspartate Synthesis
Aspartate Transaminase
-PLP
OAA + Glutamate-> Aspartate + Alpha ketogluterate
Alanine Synthesis
Alanine Transaminase
-PLP
Pyruvate + Glutamate-> Alanine + Alpha ketogluterate
Asparagine Synthesis
Asparagine Synthetase
**Adenylation
1) Aspartate-> Acyl-Adenylate Intermediate
2) NH3+ from Glutamine displaces the AMP producing Asparagine
Arginine Synthesis
1) Glutamate phosphorylated to Acyl-Phosphate intermediate
2) Acyl Phosphate intermediate is reduced to Glutamic Acid y-semialdehyde and NADPH -. NADP+
3) Glutamic acid Y-semialdehyde -> Ornithine (urea cycle) to produce Arginine
- Glutamate-> Alpha ketogluterate to provide amino group
Proline Synthesis
1) Glutamate phosphorylated to Acyl-Phosphate intermediate
2) Acyl Phosphate intermediate is reduced to Glutamic Acid y-semialdehyde
3) Nonenzymatic reaction dehydrates Glutamic Acid Y-semialdehyde and then reduced to Proline by NADPH
Serine Synthesis
1) 3-PG oxidized to 3-Phosphohydroxypyruvate
- NAD+ reduced to NADH
2) 3-Phosphohydroxypyruvate -> 3-Phosphoserine
- amino transfered from glutamate to Alpha ketoglutarate
3) 3-Phosphoserine Hydrolyzed to Serine
Glycine Synthesis
1) Serine hydroxymethyl transferase
-reversing this enzyme can be used to synthesize serine from glycine
-allows one carbon units to be synthesized from carbohydrates
Precursor: Serine
Serine + THF-> Glycine + N5,n10-methyleneTHF + H2O
2) Serine/Glycine Synthase
Precursor: NH4 + CO2
-NH4+ CO2+ N5,N10 methyleneTHF + NADH->Glycine + THF +NAD+
Cysteine Synthesis
1) Homocysteine+ Serine-> Cystathionine
- Cystathionine B-Synthase
- LOse OH and bond to S of homocystein
2) Cystathionine-> Alpha ketobutyrate + Cysteine
- Cystathioninase
Activated Methyl Cycle
Regenerates Methionine from homocysteine
1) SAM donates activated methyl group producing S-adenosyl homocysteine (
2) S-adenosyl Homocysteine is hydrolyzed
- releassing Adenosine and producing Homocysteine
3) Homocysteine is methylated via N,5methyl THF to produce methionine + THF
- Via Methionine Synthase (Homocysteine methyltransferase)
- requires methylcolbalamin derived from vitamin B12
- Some organisms use enzyme that don’t require methylcobalamin
Tyrosine Synthesis
1) Phe BH4-> Tyr + quinonoid dihydrobiopterin
- Phenyalanine Hydroxylase (monooxygenase)
- BH4-tetrahydrobiopterin-electron carrier
