Amino Acids Metabolism Flashcards
Supplies for the Amino Acid Pool
- Protein turnover - proteins salvaged and repurposed in the body
- Digested food - mostly from meat, veggies, and nuts
- De novo synthesis - synthesis of non-essential amino acids
Sources that Deplete the Amino Acid Pool
- Production of body protein
- Synthesis of nitrogen-containing compounds
- Degradation of essential amino acids
Proteolytic Enzymes
Degradation of proteins for reabsorption
Two Classes of Proteolytic Enzymes
- Exopeptidase - attacks the N or O terminus ends
- Carboxypeptidase - Attacks and adds H2O at the O end
- Aminopeptidase - Attacks and adds H2O at the N end
- Endopeptidase - attacks within the protein at a specific site
Lysosomes
Performs autophagy
Contains over 50 proteolytic enzymes
Internal environment within lysosome has a pH of 5
Proteasome
A large protein complex within the cells that breaks apart marked proteins
Marker - ubiquinitin
Ubiquitin
Marker of proteins that need to be degraded within a cell
Polyubiquitinated
Zymogens
The inactive form that most digestive enzymes are secreted
Become active when they get to their target
Ex. Trypsinogen - activated by enterokinase after getting into small intestine lumen - becomes trypsin
Essential Amino Acids
PVT TIM HALL
- Phenylalanine
- Valine
- Tryptophan
- Threonine
- Isoleucine
- Methionine
- Histidine
- Arginine
- Leucine
- Lysine
Occassionally Glutamine - depending on deficiency
Ketogenic Amino Acids
Leucine and Lysine
2:5:13
Ketogenic and Glucogenic Amino Acid
Isoleucine, Tryptonphan, Phenylalanine, Tyrosine, and Threonine
2:5:13
Glucogenic Amino Acids
Valine, Histidine, Methionine, Glycine, Arginine, Alanine, Proline, Aspartic Acid, Serine, Glutamic Acid, Glutamine, Cysteine, Asparagine
2:5:13
Why is the TCA cycle Anaplerotic?
Anaplerotic - reactions that supply intermediates for a metabolic pathway
Amino acids supply the TCA cycle with substrates if needed
Pyruvate carboxylation (requires ATP) converts pyruvate to oxaloacetate (OAA)
Reaction that Shuffles Amine groups
Transamination
Enzymes that perform transamination
Transaminases/Aminotransferase
Transaminase coenzyme
PLP (pyridoxyl-5’-phosphate)
Derivative of Vit B6
AST/ALT
Aspartate transaminase (AST) Alanine transaminase (ALT)
Used as clinical markers for liver function
Amino acids that are metabolized into alpha-ketoglutarate
Gln, His, Arg, Pro all converted to Glutamine
Glutamine is then converted into alpha-ketoglutarate
Branched Chain Amino Acid Metabolism
Valine and Isoleucine - converted to Succinyl-CoA
Leucine - Converted to Acetyl-CoA
If deficiency causes Maple-Syrup urine disease
Methionine Metabolism
Converted into Succinyl-CoA
Able to produce Cysteine
If issues in metabolism - commonly results in Homocystinuria
Threonine Metabolism
Converted into Succinyl-CoA
What two enzymes are responsible for Homocystinuria?
Homocysteine methyltransferase - converts homocysteine back to Methionine
Cystathionine-B-synthase - converts homocysteine into cystathionine (enzymes requires PLP (active form of B6)
Hyperhomocysteinemia and Homocystinuria
Usually caused by vitamins (B6, B12, or Folic Acid (B9)) or genetic disorder
Risk factor for heart disease and stroke
Treated usually with vitamin suppliments
Maple Syrup Urine Disease
Deficiency in BCKD (branched-chain alpha-keto acid dehydrogenase complex)
Inability to break down branched-chain amino acids
Presents as branched-chain amino acids in urine which gives urine a sweet smell
High prevalance in Jewish, Amish, and Mennonite populations
