Endo: Catabolism Of carbon skeleton Of AA Flashcards
AAs that don’t undergo transamination
Proline, Hydroxyproline, Lysine & Threonine “PaHaLaTa”
First catabolic reaction of AA catabolism
Removal of a-amino nitrogen by transamination
AA are converted into _________ or their precursor so that they can be metabolized to ___ & ___ or used in ______. Accounts for ____ of metabolic energy generated by animals.
CAC intermediates. CO2 & H2O. Gluconeogenesis. 10-15%.
Carbon skeletons are degraded into Pyruvate, succinyl coa, oxaloacetate or fumarate and a-ketoglurate and are therefore glucose precursor. “Pa SOFA”
Glucogenic AA
Carbon skeletons are broken down to acetyl coA or acetoacetate and can thus be converted to fatty acids or ketone bodies.
Ketogenic AA
Only ketogenic AA
Leucine
Glucogenic and Ketogenic AA at the same time
Phenylalanine, Lysine, Isoleucine, Tryptophan & Tyrosine “PLITT”
AA converted to pyruvate
Cysteine, Threonine, Tryptophan, Alanine, Glycine & Serine “CT TAGS”
AA coverted to oxaloacetate
Aspartate & Asparagine “AA”
AA converted to a-ketoglutarate
Proline, Histidine, Arginine, Glutamate & Glutamine “Pa HAGG”
AA converted to fumarate
Phenylalanine, Aspartate & Tryptophan “PAT”
AA converted to succinyl coA
Valine, Isoleucine & Methionine “VIM”
AA degraded to acetyl coA or acetoacetate
Phenylalanine, Isoleucine, Leucine, Lysine, Tryptophan, Threonine & Tyrosine “PILL T3”
Transamination forms pyruvate which can then be decarboxylated to acetyl CoA
Alanine
Splits to CO2 and NH4 and N5, N10 Methylene Tetrahydrofolate
Glycine
Transamination of glycine to ______ with Glu or Ala
Glyoxylate
Failure to catabolize glyoxylate leads to
Hyperoxaluria
Degraded to glycine and N5, N10 methylene tetrahydrofolate
Serine
Enzyme used to convert serine to pyruvate
Serine hydratase
Converted to cysteine
Cystine
Cysteine is catabolized via what pathways
Direct oxidative pathway & Transamination pathway
Enzyme used to convert cystine to cysteine
Cystine reductase
Cysteine: direct oxidative pathway
Cysteine [cysteine deoxygenase] cysteine sulfinate [transaminase] sulfinyl pyruvate [desulfinase] pyruvate
Cysteine: transamination pathway
Cysteine [transaminase] 3 mercaptopyruvate = pyruvate & 3 mercaptolactate
Cleaved to acetaldehyde and glycine
Threonine
Oxidized to acetate which is then converted to acetyl CoA
Acetaldehyde
Pathway of Threonine
Threonine [threonine aldolase] acetaldehyde [aldehyde dehydrogenase] acetate [acetate thiokinase] acetyl CoA
Transamination forms oxaloacetate
Aspartate
Undergoes hydrolysis to aspartate
Asparagine
Aspartate and Asparagine pathway
Asparagine [asparaginase] Aspartate [transaminase] Oxaloacetate
Transamination forms a-ketoglutarate
Glutamate
Undergoes hydrolysis to glutamate
Glutamine
Glutamate and Glutamine Pathway
Glutamine [glutaminase] Glutamate [transaminase] a-Ketoglutarate
Oxidized to dehydroproline which then adds water forming ___________. This is then oxidized to _______ and transaminated to _________.
Proline. Glutamate y-semialdehyde. Glutamate. a-ketoglutarate.
Proline pathway
Proline [proline dehydrogenase] glutamate-y semialdehyde [glutamate semialdehyde dehydrogenase] Glutamate = a-ketoglutarate
Converted to ornithine which then undergo transamination to glutamate-y semialdehyde
Arginine
Arginine pathway
Arginine [arginase] ornithine
Non-oxidatively deaminated then hydrated and its imidazole ring cleaved to form ___________; formimino group is then transferred to TH4 to form ______ and ______.
Histidine. N-formiminoglutamate(figlu). N-formiminoTH4 & Glutamate.
Histidine pathway
Histidine [histidinase] Urocanate [urocanase] 4-imidazolone-B-proprionate [imidazolone proprionate hydrolase] N-formiminoglutamate [glutamate formimino transferase] Glutamate = a-Ketoglutarate
Can be used to detect folic acid deficiency
Excretion of FIGLU ff. a dose of histidine
First reaction in its degradation is its hydroxylation to tyrosine
Phenylalanine
Transaminated to p-hydroxyphenyl-pyruvate followed by concerted ring hydroxylation and side chain migration to form ______ with _____ as reductant; aromatic ring opens and is hydrolyzed to ______ and _______.
Homogentisate. Ascorbate. Fumarate & Acetoacetate.
An important methyl donor
S-Adenosyl-methionine (SAM)
Condenses with ATP to form SAM
Methionine
Methionine to SAM pathway
Methionine+ATP [methionine adenosyl transferase] SAM
In methionine, removal of methyl group forms ________ which is hydrolyzed to _______ & _______.
S-adenosylhomocysteine. Adenosine & Homocysteine.
In methionine, homocysteine combines to serine to yield _______ which is subsequently forms ______ and _______.
Cystathione. Cysteine & a-ketobutyrate.
In methionine, a-Ketobutyrate is degraded to _______ & then to ______.
Propionyl CoA. Succinyl CoA.
Methionine pathway
Methionine- S adenosyl methionine- S adenosyl homocysteine- Homocysteine plus serine [cystathione synthase] Cystathione = cysteine and a-Ketobutyrate= proprionyl CoA
Isoleucine is converted to
Propionyl CoA
Valine is converted to
Methylmalonyl CoA
Methionine is converted to
a-Ketobutyrate
a-Ketobutyrate to Propionyl CoA to Methylmalonyl CoA to
Succinyl CoA
Has several pathways for degradation but the pathway that proceed via the formation ______ predominates in mammalian liver.
Lysine. Saccharopine.
Pathway of lysine involves
Transamination, oxidative decarboxylation and reactions similar to fatty acyl CoA oxidation. “TOF”
Lysine pathway
Lysine- saccharopine- aminoadipate semialdehyde- aminoadipate- ketoadipate- glutaryl CoA- crotonyl CoA- B hydroxybutyryl coA- Acetoacetyl CoA- HMG CoA- Acetoacetate
Initial reaction involves cleavage of indole ring with incorporation of 2 atoms of molecular oxygen by ________.
Tryptophan. Tryptophan oxygenase.
In tryptophan, carbon atoms of side chain and aromatic ring completely degraded via
Kynurenine-anthranilate pathway
An iron porphyrin metalloprotein. Inducible in the liver by adrenal corticosteroid and by tryptophan.
Tryptophan oxygenase
Tryptophan oxygenase feedback is inhibited by
Nicotinic acid derivatives including NADPH
Purely ketogenic AA. Degraded to _____ which is converted to _____ and ______.
Leucine. HMG CoA. Acetoacetate & Acetyl CoA.
Brached chain AA
Leucine, Isoleucine and Valine “LIV”
Shares the same first three reaction that employs a common enzyme. Resulting products are then catabolized by distinct pathways.
Branched chain AA
Same first 3 reactions shared by Branched chain AA
-Transamination to corresponding a-Ketoacids
-Oxidative decarboxylation to corresponding acyl CoA
-Dehydrogenation by FAD to form a double bond
“TOD”
Almost always associated with AA catabolism rather than AA biosynthesis. Sufficient amount of AA whether essential or non essential are present in a well balanced diet.
Amino acidopathies
Failure to catabolize AAs will result in accumulation of AA and its metabolites to the point that they become _____.
Toxic
Defect in the catabolism of ______. Deficiency in the enzyme ________. Most striking manifestation is darkening of urine d/t the presence of homogentisate. Later develops arthritis and connective tissue pigmentation.
Alkaptonuria. Tyrosine. Homogentisate oxidase.
Results in the inability to covert phenylalanine to tyrosine. Defect may be in the enzyme ________(classic PKU), ______ or ______. Major consequence is mental retardation.
PKU. Phenylalanine hydroxylase, Tetrahydrobiopterine synthase or Dihydrobiopterine synthase.
Treatment for PKU
Diet low in phenylalanine
Alternative pathways of phenylalanine catabolism
Phenylketonurics
Defect in the intestinal and renal transport of neutral AA including tryptophan. Manifest with pellagra-like s/sx because of limited conversion of tryptophan to niacin.
Hartnup disease
Defect in the absence of branched chain a-ketoacid Dehydrogenase. Odor of urine resembles maple syrup or burnt sugar. Brain damage develops unless promptly treated with ________.
Maple syrup urine disease. Diet low in BCAA.
