chapt. 39 ch. 39 student learning outcomes : explain basic synthesis of nonessential amino acids...
DESCRIPTION
Overview Degradation of amino acids Fig. 2 Overview: degradation of amino acids: A.Gluconeogenic: Pyruvate, TCA intermediates B. Ketogenic: Acetyl CoA, ketone bodiesTRANSCRIPT
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Chapt. 39
Ch. 39Student Learning Outcomes:• Explain basic synthesis of nonessential amino acids
• Uses glucose derivatives (glycolysis, TCA)• N sources often other aa
• Describe important cofactors:• PLP (from Vitamin B6) for transaminations• FH4 (tetrahydrofolate) for 1C; • BH4 (tetrahydrobiopterin) for hydroxylation
• (Phe → Tyr)• Explain general regulation of amino acid synthesis
(feedback inhibition, transcription inhibition)• Degradation of aa often distinct from synthesis path
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Overview synthesis of nonessential amino acids
Fig. 39.1*
Overview synthesis of nonessential amino acids:• Met donates the S to Cys• C skeletons come from glucose, glycolysis, TCA compounds• Aa that can be synthesized are often used for other N cmpds:
• Gly → purine, pyrimidine• Asp → purine, pyrimidine• Gln → neurotransmitter
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Overview Degradation of amino acids
Fig. 2
Overview: degradation of amino acids:A.Gluconeogenic: Pyruvate, TCA intermediatesB. Ketogenic: Acetyl CoA, ketone bodies
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Some genetic disorders of amino acid metabolismDegradation path enzyme disease symptomsPhe phe hydroxylase (PAH) PKU classic mental retardation
homogentisate oxidase alcaptonuria black urine, arthritis
Tyr fumarylacetoacetate hydrolase tyrosinemia I liver failure, deathtyrosine aminotransferase tyrosinemia II neurological
Met cystathionase cystathionuria benigncystathionine b-synthase homocystinemia cardiovascular, neurological
Gly glycine transaminase oxaluria type 1 renal failure (Gly → oxalate) Ca-oxalate stones
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Metabolism of Phe/Tyr
Fig. 39.15
Phe and Tyr:• PKU from absence PAH (autosomal
recessive); 1/104 births; all babies tested;give special diet of low Phe (essential aa)
High Phe in blood → neurological
• Tyr is made from Phevarious defects in degradation
neurological, liver failure
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Cysteine metabolism
Figs. 39.6 Cys
Cysteine metabolism:• C, N from Ser, S from Met• Met donates S to Cys via Homocys
• Removal of –CH3
• Cystathionine precursor of Cys• Feedback regulation of synthase
• Adjust for dietary Cys• Lack of synthase → homocyst(e)inemia