Amino Acid Catabolism Flashcards by Nick Mankowski

What six CAC intermediates can be made from amino acids?

A-KG

Succinyl-CoA

Fumarate

OAA

Pyruvate

(Aceto)Acetyl Coa

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Glucogenic vs. ketogenic amino acids

Glucogenic —> any amino acid whose intermediate can be converted to OAA

Ketogenic —> any whose intermediate is Acetyl-CoA or Acetoacetate

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Which amino acids make A-KG?

Arginine

Glutamate

Glutamine

Histidine

Proline

*glucogenic

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Which amino acids make succinyl-CoA

Isoleucine

Methionine

Threonine

Valine

glucogenic

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Amino acids that make fumarate and acetoacetate?

Phenylalanine

Tyrosine

both glucogenic and ketogenic

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Amino acids that make OAA

Asparagine

Aspartate

*glucogenic

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Amino acids that make pyruvate?

Alanine

Cysteine

Glycine

Threonine

Tryptophan

*both glucogenic and ketogenic

Since pyruvate can be converted to Acetyl-CoA or OAA

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Amino acids that make acetyl-CoA and acetoacetate?

Acetyl-CoA

isoleucine
leucine
threonine
tryptophan

Acetoacetate

leucine
lysine
phenyalanine
tryptophan
tyrosine
all = ketogenic

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Which amino acids are exclusively ketogenic?

Leucine

Lysine

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Which amino acids are both glucogenic and ketogenic

Threonine

Tryptophan

Tyrosine

Phenylalanine

Isoleucine

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Arginine and proline both form glutamate through which common intermediate?

Glutamate semialdehyde

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Cofactor needed to convert Histidine —> glutamate

Tetrahydrofolate (H4folate)

Enzyme: histidase

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Deficiency in histidase

Benign elevation of Histidine in the blood and urine

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Glutaminase

Glutamine —> glutamate

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Glutamine synthetase

Glutamate —> glutamine

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Arginase

Arginine —> ornithine + urea

(Last reaction of urea cycle)

*ornithine then gets converted to glutamate semialdehyde

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Glutamate dehydrogenase

Glutamate —> a-KG

Important methyl donor compound involved in the methionine pathway…and subsequent compounds before intermediate

Homocysteine

S-adenosylmethionine (SAM)

After donates CH3 =
S-adenosylhomocysteine (SAHC)

Met —> SAM —> SAHC —> homocysteine

2 possible fates of Homocysteine

Converted back to Met, to regenerate SAM in a reaction requiring H4folate and vitamin B12 (Cobalamin)
Continue down pathway to succinyl-CoA

Homocystinuria

(-) cystathionine beta-synthase

Rxn: Homocysteine —> alpha-ketobutyrate
(Common intermediate with Threonine)

Cofactors = PLP and B6

Build up of HC and Met

Inborn error of metabolism

Faulty bone development, mental retardation, as well as complications in muscle and CT

Treatment: high vitamin B6, and low Met diets…but cannot reverse mental shit

Alpha-ketoacid dehydrogenase

*Alpha-ketobutyrate —> propionyl-CoA

Met pathway

= Met and Threonine intermediate

Propionyl-CoA = intermediate for Met, Thr, Val, and Isoleucine

Cofactors needed to convert propionyl-CoA —> methylmalonyl-CoA

Biotin

Methylmalonyl-CoA —> succinyl-CoA

Methylmalonyl-CoA mutase

Vitamin B12

Methylmalonic acidemia

(-) methylmalonyl-CoA mutase

Build up of methylmalonic acid in blood and urine

Inborn error of metabolism

May also be an increase in propionyl-CoA —> making acidemia worse

Failure to thrive, vomiting, dehyrdation, developmental delay, seizures, hyper-NH4+, and progressive encelphalopathy

**can also be caused by severe B12 deficiency (cofactor)

Branched-chain aminotransferases

Converts branched amino acid to its corresponding ketoacid Isoleucine, valine, leucine

MSUD

(-) branched-chain alpha-ketoacid dehydrogenase complex Build up of ketoacids in urine —> maple syrup smell Severe abnormal brain, mental retard, infant death

How is SAM generated

Transferring adenosine from ATP —> Met

Methionine synthase

Homocysteine —> methionine Requires H4folate and vitamin B12

OAA pathway

Asparagine —> aspartate (asparaginase) Aspartate —> OAA (aspartate aminotransferase, PLP) .... with a-KG —> glutamate

Alanine aminotransferase (ALT)

Tryptophan —> alanine Alanine —> pyruvate (ALT)

Threonine —> | ?amino acid and acetyl-CoA

Glycine Pyruvate pathway

Steps from threonine —> pyruvate

Threonine —> glycine + Acetyl-CoA Glycine —> serine —> pyruvate

What important cofactor is produce from the glycine —> serine reaction In the pyruvate pathway

H4folate

Cysteine —> what CAC intermediate | 2 steps

Pyruvate

Phenylketonuria (PKU)

(-) phenylalanine hydroxylase Rxn: Phen —> Tyr One of most common amino acid metabolism disorders Retard in newborns Buildup of phenyl...interferes with normal neurotransmitter production Restrict phenyl in diet

Hyperphenylalaninemia

Deficiencies in either the BH4 synthesis or regeneration from BH2 BH4 —> BH2 during phenyl —> tyrosine reaction Dihydropteridine reductase: BH2 —> BH4 Symptoms similar to PKU ... but causes and treatment differ

Tyrosinemia Type II

(-) tyrosine aminotransferase Tyrosine —> p-hydroxyphenylpyruvate Build up of tyrosine Mental development shit Visual problems Retardation

Alcaptonuria

(-) homogentisate oxidase Homogentisate —> maleylacetoacetate Build up of homogentisate Turns urine a dark brown color upon contact with air Relatively benign disease, but can cause premature arthritis later in life

Tyrosinemia Type I

(-) fumarylacetoacetate hydrolase Cleaves fumarylacetoacetate —> fumarate and acetaacetate Build up of sustrate... Urine a cabbage like odor, If severe results in liver failure and renal tubular acidosis, Treatment = restrict phenyalanine and tyrosine from diet

Argininemia

(-) ariginase Defective urea synthesis Mental retardation

Argininosuccinic acidemia

(-) Argininosuccinase Defective urea synthesis Vomiting, convulsions

Carbamoyl phosphate synthase 1 deficiency

(-) CPS1 Defective urea synthesis Lethargy, convulsions, early death