amino acid synthesis Flashcards
OAA can be synthesized from what 2 amino acids directly?
aspartate and asparagine
Pyruvate can be synthesized by what 3 amino acids?
alanine
serine (from glycine)
cysteine
What enzyme catalyzes asparagine to aspartate?
Asparaginase, transfer of NH4+
What enzyme catalyzes aspartate to OAA?
AST (alanine aminotransferase), requires co-factor PLP
What enzyme catalyzes glutamine to glutamate?
glutaminase, transfer of NH4+
What 3 amino acids can be used to synthesize glutamate?
proline, histidine, arginine
What enzyme catalyzes aspartate to asparagine?
asparagine synthetase
What enzyme catalyzes aspartate to OAA?
AST (aspartate aminotransferase)
What enzyme catalyzes serine to glycine (reversible)?
serine hydroxymethyl transferase, requires co-factor PLP
All aminotransferases require what co-factor?
Vitamin B6, PLP (pyridoxal 5’-phosphate)
Synthesis of serine starts with what as substrate?
3-phosphoglycerate (from glycolysis)
What molecule serves as amino group donor for keto-acid?
glutamate
What molecule serves as amino group acceptor for the corresponding amino acid?
alpha-ketoglutarate
phosphoglycerate dehydrogenase
3-phosphoserine aminotransferase
phophatase
enzymes involved in the synthesis of serine
What are the essential amino acids?
PVT TIM HALL Phe Val Thr Trp Iso Met His Arg Leu Lys
What is generated by transamination of alpha-ketoglutarate and by deamidation of glutamine.
glutamate
Tyrosine is formed from what amino acid and by what enzyme? What co-factor is needed?
phenylalanine, phenylalanine hydroxylase, co-factor THBtn
What is formed from serine and the essential amino acid methionine?
cysteine
What is the major source of one-carbon groups in the one carbon pool?
serine
Describe the synthesis of methionine from homocysteine. Why is this reaction important?
homocysteine + N5-methyl-THF»_space; methionine + THF
Enzyme: methionine synthase
Co-factor: B12
**only reaction that converts the most reduced form of THF (N5-methyl-THF) back to THF
Describe the synthesis of cysteine from homocysteine.
1) homocysteine + serine>>cystathionine Enzyme: cystathionine beta-synthase Co-factor: PLP (Vit. B6) 2) cystathionine>>cysteine Enzyme: cystathionase
Where are branched-chain aminotransferases located?
skeletal muscles
What are the three branched-chain amino acids (BCAAs)?
Valine, Isoleucine, Leucine
What is the function of branched-chain aminotransferases?
convert BCAAs to their corresponding branched-chain keto-acids
branched chain alpha-ketoacids are decarboxylated by what in the liver and other tissues?
branched-chain alpha-ketoacid dehydrogenase complex (BCKDH)
What products are produced by BCKDH?
branched chain acyl-CoAs
What acyl-CoA does the catabolism of valine produce?
propionyl-CoA
What acyl-CoA does the catabolism of isoleucine produce?
propionyl-CoA and acetyl-CoA
What acyl-CoA does the catabolism of leucine produce?
acetyl-CoA
