Amino Acid Oxidation Pathways Flashcards by Roberta Davidsson

Fates of Carbon skeleton

Complete oxidation in TCA cycle to CO2 and H2O
Gluconeogenesis
Ketoneogenesis

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AAs forming pyruvate

ALA
CYS
GLY
SER
THR
TRP
-glucogenic

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AAs forming OAA

ASN
ASP
-glucogenic

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AAs forming Fumarate

PHE
TYR
-glucogenic

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AAs forming Succinyl CoA

ILE
MET
THR
VAL
-glucogenic

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AAs forming alpha-KG

GLU
ARG
GLN
HIS
PRO
-glucogenic
(all first to Glu)

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AAs forming Acetyl CoA

PHE
THR
ILE
TRP
TYR
-both glycogenic and ketogenic
LEU
LYS
-ketogenic

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Serine

sphingosine - sphingolipids
ethanolamine
choline

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Glycine

purine synthesis
heme biosynthesis
conjugated bile acids

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Glycine cleavage enzyme deficiency

nonketotic hyperglycinemia
mental deficiency
early death

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Phenylketonuria PKU

deficiency in Phe hydroxylase
ketoacidosis
mental retardation
–Phe free diet

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Histamine

His -> histamine + CO2
enzyme: His decarboxylase
vasodilation, allergic reaction, stimulation of HCl secretion to stomach

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Cystathione synthase deficiency

hyperhomocysteinemia

atherosclerosis

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Methylmalonic aciduria

deficiency of vitamin B12

deficieny of methylmalonyl mutase

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Branched chain AAs

breakdown in muscle, kidney, adipose tissue, brain
special enzyme: BCAT - branched chain aminotransferase
-not in liver
-simple transamination, producing alpha-ketoacids
Val, Ile, Leu

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Breakdown of Valine

Val- BCAT - 2ketoisovalerate - BCalphaKADH -Isobutyryl CoA - Proprionyl CoA
requires TPP, lipoid acid, CoASH, FAD and NAD+

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Breakdown of Isoleucine

Ile - BCAT - 2keto3methyl valerate - BCalphaKADH - 2methylbutyryl CoA - Proprionyl CoA + Acetyl CoA
requires TPP, lipoid acid, CoASH, FAD and NAD+

Breakdown of Leucine

Leu - BCAT - 2ketoiso caproate - BCalphaKADH - Isovaleryl CoA - Acetoacetate + Acetyl CoA
requires TPP, lipoid acid, CoASH, FAD and NAD+

Regulation of BC alpha KADH

covalent:
activation - protein phosphatase (activated by high BCAA in diet)
inhibition - protein kinase (activated by low BCAA in diet)

Deficiency in BCKD

maplesyrupurine
ketoacidosis
mental retardation

Asparagine -> OAA

Asn - ASPARAGINASE - Asp - ASPARTATE AMINOTRANSFERASE - OAA

requires PLP

Threonine -> Pyruvate

Thr - THREONINE DH - 2amino3ketobutyrate - Gly - SERINE HYDROXYMETHYL TRANSFERASE - Ser - SERINE DH - Pyruvate
requires MTHF

Tryptophan -> Pyruvate

Trp - Ala - ALANINE AMINO TRANSFERASE - pyruvate

requires PLP

Tryptophan + Lysine -> Acetyl CoA

Trp / Lys - alpha ketoadipate - glutaryl Coa - Acetoacetyl Coa - B KETOACYL COA TRANSFERASE - Acetyl CoA

Phenylalanine -> Acetyl CoA

Phe - PHENYLALANINE HYDROXYLASE - Tyr - Acetoacetate - Acetoacetyl CoA - B KETOACYL COA TRANSFERASE - Acetyl Coa requires THF and O2

Leucine -> Acetyl CoA

Leu - Acetoacetate - Acetoacetyl CoA - B KETOACYL COA TRANSFERASE - Acetyl CoA or straight to acetyl coa

Isoleucine -> Acetyl CoA

straight to acetyl Coa

Threonine -> Acetyl CoA

Thr - THREONINE DH - 2amino3ketobutyrate - 2AMINO 3KETOBUTYRATE COA LIGASE - Acetyl Coa

Arginine -> alpha Ketoglutarate

Arg - ARGINASE - ornithine - ORNITHINE delta AMINOTRANSFERASE - glutamate gamma semialdehyde - GLUTAMATE SEMIALDEHYDE DH - Glu - GLUTAMATE DH - alpha KG occurs primary in liver

Proline -> alpha Ketoglutarate

Pro - PROLINE OXIDASE - Pyrroline 5 carboxylate - glutamate gamma semialdehyde - GLUTAMATE SEMIALDEHYDE DH - Glu - GLUTAMATE DH - alpha KG

Glutamine -> alpha Ketoglutarate

Gln - GLUTAMINASE - Glu - GLUTAMATE DH - alphaKG | requires PLP, NADPH/NADH

Histidine -> alpha Ketoglutarate

His - HISTIDINE AMMONIA LYASE - urocanate - UROCANATE HYDRATASE - 4 imidazolone 5 proprionate - IMIDAZOLONE PROPRIONASE - N-formimino glutamate - GLUTAMATE FORMIMINO TRANSFERASE - Glu - GLUTAMATE DH - alpha KG reguires THF

Methionine -> Succinyl CoA

Met - METHIONINE ADENOSYLTRANSFERASE - 5adenosyl methionine sam - 5adeonosyl homocysteine sah - HYDROLASE - homocysteine - CYSTATHIONINE B SYNTHASE - cystathionine - CYSTATHIONINE GAMMA LYASE - alpha ketobutyrate - a KETOACID DH - proprionyl coa - d-methylmalonyl coa -l-methylmalonyl coa -Succinyl coa

Threonine -> Succinyl CoA

Thr - THREONINE DEHYDRATASE - a ketobutyrate - aKETOACID DH - proprionyl coa - methylmalonyl coa - succinyl coa

Isoleucine -> Succinyl CoA

Ile - proprionyl coa - methylmalonyl coa - succinyl coa

Valine -> Succinyl CoA

Val - proprionyl coa - methylmalonyl coa - succinyl coa

Metabolism of Glu related neurotransmitters

Glu - GLUTAMATE DECARBOXYLASE - GABA - AMINO TRANSFERASE - succinate semialdehyde - SUCCINATE SEMIALDEHYDE DH - succinate

Arginine related compounds

Arg -> NO synthesis Arg -> Orn -> polyamines Arg - Creatine -CREATINE KINASE - creatine P - creatinine

Biogenic amine of tyrosine

Tyr - TYROSINE HYDROXYLASE - DOPA - DOPA DECARBOXYLASE - dopamine - DOPAMINE B HYDROXYLASE - norepinephrine - NE N METHYL TRANSFERASE - epinephrine

Biogenic amine of Tryptophan

Trp - TRP HYDROXYLASE - 5hydroxy Trp - AROMATIC AA DECARBOXYLASE - serotonin

MAO (monoamine oxidase)

in neural + other tissues | deaminates/ inactivates neurotransmitters

Serotonin

synthesized mostly in intestinal mucosa degraded by MAO pain perception, regulate sleep, apetite, temperature, blood pressure, cognitive functions, mood