Protein Metabolism Flashcards
What are the two main sources of Proteins?
Dietary and Intracellular
What are the three main drivers of protein oxidation?
1-Normal synthesis and degradation
2-Protein rich diet
3-Starvation or diabetes mellitus
What are the 3 major zymogen proteases released from the pancreas?
1-Trypsinogen (Trypsin)
2-Chymotrypsinogen (chymotrypsin)
3-Procarboxypeptidase A and B (Carboxypeptidase A and B)
What two signals from intestinal cells are important for protein degradation?
1-Secretin (stimulate bicarbonate)
2-Cholecystokinin (CCK-stimulate zymogen release)
What are the three main fates of amino acids once they are absorbed?
1-Sythesis of other proteins
2-Catabolized for energy
3-Transported to liver and excreted
Where does most of protein catabolism take place?
Liver
What are the four important “Nitrogen shuttle” amino acids?
1-Glutamate (N acceptor)
2-Glutamine (N acceptor)
3-Aspartate (Amine shifter)
4-Alanine (Amine shifter)
Why is ammonia toxic?
Disrupts astrocyte K+ uptake causing high extracellular K+ thus preventing GABA inhibition. Cells are then more excitable and result in hyperactivity, seizures, etc.
What are the two common amino acid catabolism reactions?
1-Transaminase rxns (transfer amine group)
2-One-Carbon Transfers
How is intracellular ammonia buffered?
Converting Glutamate to glutamine
What two ways is nitrogen transported to the liver?
1-Gutamine transport
2-Glucose-Alanine cycle (Nitrogen moves in the form of Alanine)
What purpose does the Urea cycle serve?
Excrete liver nitrogen
What is the “backbone” amino acid of the Urea Cycle?
Ornithine
Glutamine is the form of Nitrogen that typically arrives from the?
Vasculature and other tissues
Alanine is the form of Nitrogen that typically arrives from the?
Muscles
The conversion of Amino acids into Carbamoyl phosphate takes place where?
Mitochondrial matrix
What are the two main ways to regulate the urea cycle?
1-Increase synthesis of the 4 main enzymes of the Urea cycle
2-Allosteric regulation of Carbamoyl phosphate synthetase I
What are the 4 main enzymes of the urea cycle?
1-Ornithine Transcarbomoylase
2-Arginosuccinate synthetase
3-Arginosuccinase
4-Arginase
What process is an important linker between the Citric and Urea cylcles?
Aspartate-argininosuccinate shunt
What three cofactors (Vitamins) are important in one carbon transfer reactions?
1-Biotin
2-Tetrahydrofolate
3-Adenosylmethionine
Which 6 amino acids are degraded to pyruvate?
1-Tryptophan 2-Threonine 3-Alanine 4-Cysteine 5-Serine 6-Glycine
Which 7 amino acids degrade to acetyl-CoA?
1-Tryptophan 2-Tyrosine 3-Threonine 4-Isoleucine 5-Leucine 6-Lysine 7-Phenylalanine
Which five amino acids are degraded to a-ketoglutarate?
1-Glutamate 2-Glutamine 3-Arginine 4-Proline 5-Histidine
Which four amino acids are degraded to succinyl-CoA?
1-Valine
2-Isoleucine
3-Threonine
4-Methionine
