AA Metabolism Flashcards
What is the major proteolytic enzyme in the stomach?
What is the inactive form of this enzyme
Pepsin
Pepsinogen
What cells in the stomach produce Pepsin
What cells produce HCL
Chief cells
Parietal cells
How is pepsinogen activated?
HCl secreted by the stomach
At low energy states what are AA converted to?
- AA are converted to pyruvate and enter gluconeogenesis to form Glucose.
- They can also be converted to Acetyl Coa to be oxidized in the CAC to H20 and C02.
- They can form Ketone Bodies in times of starvation.
In the low energy state are AA being synthesized?
No
At high energy levels what is the fate of the blood pool of AA?
- Glycogen can be formed after conversion to glucose.
2. Fatty Acids can be formed via conversion to Acetyl CoA
What is the purpose of the AA pool?
6 Things
- Ensures availability of AA to tissues for protein synthesis.
- Vital Proteins listed in the next slide.
- Generates glucose and ketone Bodies.
- Can be oxidized in TCA cycle
- They Mantain Blood pH
- They can be made into Fatty Acids
What are important structures derived from AA in the body?
Proteins, Neurotransmitters, Heme, Pyrimidines, Purines, Creatine Phosphate, Melanin, skin Pigment, Nucleotides, Nuclaic Acids,
What is the average dietary protein intake per day?
What is the other source of AA for proteins in the body.
100 g / day
Protein turnover from AA found in the body. Proteins that have been degraded by endocytosis, phagocytosis, ubiquitin targeted degradation.
What is the average turnover of endogenous protein?
3-600g / day
What are common proteins that undergo synthesis and degradation frequently?
Heme, Muscle Protein, Digestive enzymes, Cells lining the GI tract.
How are pancreatic enzymes activated?
When the pH of the intestines is raised from Bicarbonate release.
Must digestive enzymes be activated?
Yes, digestive enzymes are produced as inactive precursors (Zymogens)
How are pancreatic zymogens activated?
Enteropepsidase converts Trypsinogen to Trypsin…. Trypsin activates Chymotrypsinogen, Proelastase, Procarboxypepsidase,
Can essential AA be synthesized?
What are two you should remember from lecture?
No
Methionine and Phenylalanine.
What are nonessential AA?
Nonessential amino acids are synthesized from common metabolic intermediates or from other amino acids.
What are Cysteine and Tyrosine produced from?
Methionine and Phenylalanine respectively.
What gives rise to Kwashiorkor Syndrome?
Deficiency of an AA in the diet.
- Results in Decreases plasma concentration of Proteins. Albumin and Transferin indicate starvation.
- Increased interstitial fluid adema. due to increased osmotic pressure.
- Adema results in a distended belly
- Inability to produce digestive enzymes and replenish intestinal mucosa cells.
What are the 4 fates of AA in the blood?
- New Protein Synthesis
- Conversion to Pyruvate and Acetyl CoA
- Degraded to enter the urea cycle
- Functional products, Signaling peptides, pyrimidine, purine, ect.
What factors affect the rate of protein degradation?
- Hormonal Control
2. Other methods (lyosomal degradation, protein denaturation)
How is protein degradation hormonally regulated?
Glucocorticoids released from the adrenal glands increase protein degradation in the muscle tissue via an increase in ubiquitin production. and proteolysis via the proteosome pathway.
Excessive thyroid hormones increase protein turnover.
Insulin increases protein synthesis.
What are two methods of non- hormonal regulation of AA
- Lyosomes can be activated and will increase protein degradation.
- Proteins can be denatured which will cause them to loose function.
What amino acid sequence activates the ubiquitone- proteosome pathway?
PEST- Regions rich in Pro (P), Glu (E), Ser (S), and Thr (T)- short half life and degraded by ubiquitin-proteosome pathway
What N-Terminal Residues will make a protein unstable?
N-terminal residues - The presence of Phe, Leu, Asp, Lys, or Arg at N-terminal makes protein unstable
What is an example of oxidative damage to a protein?
Lys Oxidation
How can proteins be modified?
Mutations and deletions
What digestive enzymes are found in pancreatic secretions?
6
"B E C E E P" Bicarbonate. - Endopepsidase- Chymotrypsin- Elastase- Exopeptidases- Proteases-
How can Cystic Fibrosis affect digestion?
Decreased Na+ secretion through CFTR channels results in extreamly thick secretions in the pancreas which will occlude the pancreatic ducts.
What are the three ways AA are transported into the cells of the intestine?
- Na Dependent Carrier transport
- Facilitated Transport
- y-Glutamyl Cycle in the intestine and kidney
How does secondary active transport of AA using the Na+ gradient work?
- Co-transport Na+ and the amino acids from the outside of the apical membrane to the inside is driven by low intracellular [Na+] that results from the pumping of Na+out of the cell by Na+/K+ ATPase
- Facilitated transporters in the serosal membrane transport amino acids to portal vein.
