Flashcards in Protein and AA metabolism Deck (17):
where do the amino acids in the "AA pool" come from?
the AA come from dietary intake, protein turnover inside the body, and de novo synthesis of new nonessential AA inside the body
Where do the amino acids in the "AA pool" go?
Approximately the same amount that came from protein turnover inside the body go back into the body, some AA are used to synthesize creatine, neurotransmitters, nucleotides, and some go into the pathways that create glucose/glycogen, CO2, urea, ketone bodies, fatty acids and steroids depending on metabolic needs
exopeptidase is a proteolytic (degrades protein) by attacking the C (carboxypeptidase) or N (aminopeptidase) terminus of the protein
Think exo = attacks at end, shortens proteins
proteolytic enzyme that attacks within the protein at internal peptide bonds
endo = inside attack, splits proteins
intracellular proteolytic control (2 ways)
1) lysosomes house over 50 hydolase-type proteolytic enzymes that are non-selective, but function at 5pH (found inside lysosome). These enzymes are non functional at cytosolic pH7. When a protein is sent/enters the lysosome it will get degraded.
2) there are also large proteasome complexes in the cytosol that cleave polyubiquinated (marked for degradation)
extracellular proteolytic control
inactive forms of proteolytic enzymes (zymogens) are secreted as needed and are only activated by enterokinase which is found on the small intestinal epithelial cell surface
Essential AA (10)
Met, Thr, Val, Phe, Ile, Trp, Lys, Leu, His, Arg
just ketogenic AA
just glucogenic AA
Leu, Lys = "fat Loss in keto diet)
Ile, Trp, Phe, Tyr, Thr = "I wipe with TP"
all the rest of the AA
what do transaminase reactions do?
these rxns (enzyme also called aminotransferases) shuffle the amino group from an AA to an alpha-ketoacid (ie a-ketoglutarate) and are coupled reactions/reversible between a-ketoacids and AA.
These reactions require PLP which is a derivative of vitamin B6 so would be effected by a B6 deficiency
hyperhomocysteinemia and homocysteinemia
are deficiencies in B6, B12 and/or folic acid OR are genetic defects in cystathionine B-synthase needed for methionine degradation (makes homocysteine).
risk factors for heart disease (atherosclerosis)/stroke/lens dislocation/osteoperosis
corrected via vitamin supplements
maple syrup urine disease
maple syrup urine smell, BCAAs accumulate in blood, higher in mennonite, amish, jewish communities
PKU is caused by deficiency in phenylalanine hydroxylase (PAH)
disrupted neurotransmission and impaired myelin formation = severe brain impairment
severe lack of melanin caused by defects to tyrosinase enzyme (usually would convert tyrosine to melanin)
absence of skin/hair/eye pigmentation
removes nitrogen from body by making urea or ammonia
in the brain nitrogen (NH4+) is removed in the form of Glu (glutamate) and Gln (glutamine) since Gln can cross BBB into blood and into liver
in tissues nitrogen (NH4) is removed as Gln and Ala since Ala can cross into blood supply and into liver
also known as the urea cycle
happens in liver mitochondria and cytosol. creates urea (that is sent to kidneys via blood for excretion)
liver failure or urea cycle failures can lead to increase toxic ammonia levels which cause pH imbalances in the brain and lead to cerebral edema/intracranial hypertension. inhibits glutamate dehydrogenase (in TCA) which depresses ATP production. neurotoxicity