Amino Acid Metabolism Flashcards
What is the Amino Acid Pool and where do these AAs come from?
The come from Protein turnover from misfolded proteins being broken down, digested food that has been absorbed by small intestine, and de novo synthesis.
What are proteolytic enzymes? Give specific examples of Exopeptidases and endopeptidases.
Proteolytic enzymes are enzymes that cleave proteins. Based on the specific part, there are exopeptidases and endopeptidases.
Exopeptidases–> cleave on either the N terminus exopeptidases or the C terminus exopeptidases.
N-terminus: aminopeptidases
C-terminus: carboxypeptidases
What are lysosomes and at what pH are they activated?
Lysosomes are intracellular organelles that degrade protein via hydrolysis. They are the most active at pH=5 and inactive at pH=7.
What are the different types of methods that a lysosome will have to try and target degradable proteins?
They have non-selective and selective means:
Non-selective: macroautophagy, microautophagy, charperone-mediated autophagy
Selective: via Endocytosis and MVB Pathway
What are the different methods that a cell will use to degrade older proteins or mis-folded proteins?
- ) lysosomal degradation
2. ) proteosome degradation
What is the proteosome and how does it work?
The proteosome is a large protein complex consisting of 19s, 20s, 19s subunits ( 19s= regulatory, 20s= catalytic).
The process by which it works is through electrostatic interaction between 19s subunit with UBIQUITIN protein to bind to the proteosome for degradation.
What is the connection between the proteosome and the Urea Cycle? Other catabolic processes?
The proteosome will break down proteins to the basic sub-units: a.) NH3 b.) carbon skeleton c.) Ubiquitin
Carbon Skeleton–> TCA cycle, Glycolysis, etc.
NH3–> Pushed out via the Urea Cycle by using CPSI shuttle in the mitochondria that helps create carbamoyl-P.
**That is added to ornitate–> citrulline–>aspartosuccinate–> arginine (fumarate leaves)–> ornithine (Urea leaves)
What amino acid residue helps link Ubiquitinated protein to the proteosome?
Lysine residues via polar, electrostatic interactions
what happens in MACRO-LEVEL extracellular proteolytic cleavage?
-proteolytic enzymes secreted as needed based on what the organism eats (small intestine digestion)
- usually secreted in inactive zymogen forms:
small intestine lumen (enterocytes) that secrete peptidases–> cleavage of trypsinogen to trypsin enzyme
–> leads to the breakdown of a lot of other proteolytic enzymes like chemotripsinogen–> chemotripsin
Tell me all of the Essential Amino Acids?
PVT TIM HALL
Phenylalanine
VALINE**
Threonine
Tryptophan
ISOLEUCINE**
Methionine
Histidine
Arginine**
Leucine
Lysine
Tell me all the ketogenic amino acids? (2)
Leucine & Lysine
Tell me all the ketogenic & glucogenic amino acids? (5)
Tryptophan, Tyrosine, Phenylalanine, Isoleucine, Threonine
All “T” Amino acids, All “aromatic” amino acids, and Isoleucine
What is oxidative deamination and where does it take place?
Oxidative deamination is the conversion of an amide to a ketone via the use of Glutamate Dehydrogenase (GDH) which converts:
Glutamate–> Alpha-KG + NH3
Oxidative Deamination is the step used in the liver to create free standing NH3 to enter Urea Cycle. First transamination of unwanted AA occurs, followed by formation of its base keto-acid.
NH3–> CPSI–> Carbamoyl-P
carbamoyl P enters Urea cycle and binds with ornithine
What is the name of the cofactor essential for transaminase enzymes?
Pyrridoxyl- 5’-phosphate which is a derivative of Vitamin B6
What is the clinical relevance of ALT (Alanine Transaminase) and AST (aspartate transaminase)?
ALT and AST are specific transaminases that are used to determine liver disease or liver damage. The increase in the level of these transaminases suggest increased permeability in hepatocytes–> release of Transaminase Proteins.
