9. Protein and Amino Acid Metabolism Flashcards
Where does exopeptidase munch protiens?
What about endopeptidase?
Exo = outside (C or N terminus)
Endo = Inside (Somewhere in the middle; internal peptide bonds)
What pathway is used for proteasomal degradation?
Ubiquitin pathway (Protiens are marked by ubiquitin for degradation by a proteosome)
Where do the amino groups from protien breakdown go?
To the urea cycle!
What happens to the carbon skeletons in protein degradation?
They are used for energy - either storage as glucose / glycogen / fatty acid synthesis or as cellular respiration products (TCA cycle)
What is the job of enterokinase?
Extracellular proteolysis
It’s found in the small intestine, where it activates trypsin, which activates chymotrypsin.
What amino acids are not Glucogenic?
Leucine / Lysine
(Gluconeogenesis is for winners and these AAs are L-osers)
What amino acids can be either glucogenic or ketogenic?
Phenylalanine
Isoleucine
Tryptophan
Tyrosine
Threonine
(They have to do TWO jobs? That’s the PITTTs!)
What important products come from Phenylalanine?
Tyrosine ⇒ Epinephrine, Thyroid Hormones, Dopamine
What important coenzyme do transaminases require?
PLP (pyridoxyl-5’-phosphate)
-derived from pyridoxine-
What are the clinically relevant transaminases, and what are they used for in the body?
What about a clinical setting?
ALT / AST - both used for Glutamate ⇔ alpha-ketoglutarate reactions
Used as liver funciton markers
What kind of amino acids cannot be degraded in the liver?
Where are they degraded?
What specific amino acids are they?
Branch-Chain Amino Acids
Muscle, Kidney, Brain
Valine, Leucine, Isoleucine
Other than transaminases, what important amino acid metabolic enzyme requires PLP?
What disease is associated with its deficiency?
cystathionine beta-synthase
It catalyzes homocystine ⇒ Cystathionine, and its deficiency causes homocystinuria.
Maple Syrup Urine disease is caused by a buildup of what kind of amino acids?
What is the deficient enzyme?
Branched chain
Branched Chain alpha-ketoacid Dehydrogenase
People who pay attention to Phenylketonurics labels might have a deficiency in which enzyme?
Phenylalanine Hydroxylase
What amino acid is made into the following?
Epinephrine
Thyroid Hormones
Dopamine
Melanin
Tyrosine
What amino acid is made into the following?
Serotonin
Melatonin
Niacin
Tryptophan
What amino acid is made into Acetylcholine?
Serine
What two amino acids are used to remove ammonia in the brain?
Glutamate / Glutamine
What two amino acids are used to remove ammonia in the tissues (not the brain)?
Alanine / Glutamine
(The G bros are the ammonia pros, but the tissues can’t afford both - so they just get glutamine and this guy Al from off the street)
What aspect of ammonia’s toxicity might be most important to Dr. Agbas?
Its ability to cause mitochondrial dysfunction.
It can also permeate membranes to get to the mitochondria.
What three amino acids make Creatine?
Methionine
Arginine
Glycine
(MAGazine for storing energy)
In regards to ALT
What two Ketoacid/Amino acid complexes are changed between?
ALT
Pyruvate + Glutamate -> alpha-ketoglutarate + Alanine
(ALT is ELITE so it gets Pyruvate, AL- in ALT stands for Alanine. Both use Glutamate / Alpha-KetoGlutarate)
In regards to AST
What two Ketoacid / Amino Acid complexes are switched between?
AST
Oxaloacetate + Glutamate <-> Alpha-Ketoglutarate + Aspartate
(AST - A Second-rate Transaminase gets the last product of TCA on one end, and the ASS(partate) end of the amino acid deal on the other)
The disease Alkaptonuria (Ochronosis) is caused by a deficiency of what enzyme?
Homogentisate Oxidase
Heme can be derived from what Amino Acid?
Glycine
What amino acid gives rise to Thyroid Hormones?
