Protein Digestion-nitrogen metabolism-urea cycle
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- positive nitrogen balance
- insulin world - anabolism
- negative nitrogen balance
- glucagon world - catabolism
- Enzyme that breaks up protein in stomach
- pepsin
- Protein digestion in upper intestines
- bicarb + proteases break peptides into AA or di & tripeptides (anything larger would produce Ab response in blood)
- Proteases are _________
- zyminogens
- zyminogen
- proteases are activated by cleavage
- Cascade of protyolitic activation
-
Pepsinogen activated by high pH of stomach.
Trypsinogen activated by enteropeptidase (master key) into trypsin. Now tripsin (2nd key) activates all other enzymes (chymotrypsinogen, proelastase, procarboxypeptidase) - Where is enteropeptidase located?
- wall of small intestine (damage can result in problems w/ protease activation)
- why do we have so many enzymes in gut
- each have particular specificity
- Where do transporter proteins for amino acids exist?
- intestinal luman and kidney
- transporter proteins often work on specific amino acids T/F?
- T
- Nitrogen metabolism exists mostly in ______ world.
- glucagon world
- Where do 2 N in urea come from?
-
One as free N in form of ammonium
Other as N from aspartate - transamination
- transfer of nitrogen. take an amino acid and turn it into alpha keto acid
- cofactor used in transamination
- PLP (vB6)
- pyradoxal phosphate (B6)
- enzyme that catalyzes transaminatin by accepting ammonium ion
- glutamate-oxaloacetate transaminase/aspartate amino transferase (SGOT/AST)
-
transamination rxn
marker for liver damage
4C-5C
uses glutamate as N carrier - glutamate pyruvate transaminase/alanine aminotransferase (SGPT/ALT)
-
transamination rxn
enzyme is marker for liver damage
3C-5C
uses glutamate as N carrier - extracellular carrier of N
- alanine
- intracellular carrier of N
- glutamate
- What are sources of NH4+ (for urea) in liver :
- 1 free NH4+ & 1 from aspartate
- Glutamate dehydrogenase
- Takes N off glutamate (oxidative deamination) generating ammonium ion, NADPH, and a - ketoglutarate
-
hyperammonemia I
1) enzymes involved
2) clinical signs & syptoms
3) differential -
ornathine transcarbamolase
ammonia levels will rise, BUN is going to go down as , glutamine is going to go up)***increase in uracil or orotic acid*** -
hyperammonemia II
1) enzymes involved
2) clinical signs & syptoms
3) differential -
carbamoyl phosphate synthetase-
ammonia levels will rise, BUN is going to go down as , glutamine is going to go up***NO increase in uracil or orotic acid)*** - urea precursors
-
amino acids
glutamate
aspartate
NH4+ - N- acetyl glutamic acid
-
+ affector of urea cycle
stimulates CPS I enzyme - Breakdown of AA takes place in peroxisome because
- products are a-keto acid, H2O2 (toxic), and amonium ion
- glutamine
- can carry 2 N instead of just 1
- Ammonia Toxicity
- Ammonia level greater than 10 mgms/L is toxic to the cells
- Ammonium Ion Blood level
- 0.5 mg/L
- glutamine intracellular or extracellular
- can be intracellular or extracellular carrier
- intestinal cells have high concentrations of _______
- glutamine (cuz rapidly dividing)
- why do kidneys have high concentrations of glutamine
- detoxification
- carbamyl phosphyl sythetase 1 (CPSI)
- found in mitochondria - ratel limiting step in protein digestion
- importance of ornithine & citruline
- can cross mitochondrial membrane