Protein Digestion Flashcards
sources of amino acids
- body protein (major source)
- dietary protein
- digestive enzymes
uses for amino acids
- synth of nitrogen containing compounds
- degradation for energy to make glucose
- protein synth
- poop production
what concentration are amino acids maintained at in the blood
-high for use all over the body
two sources of blood protein
- 3/4 body breakdown
- 1/4 dietary
dietary protein digestion
- glands of the stomach secrete acid and pepsinogen
- acid denatures proteins and pepsin produces peptides
- peptides eneter the small intestine, pancreas secretes bicarb and zymogens
- activated enzymes in the duodenum digest long peptides into short ones
- enzymes of intestinal lumen and villi produce mostly amino acid for absorption
pepsinogen
- is not active at neutral ph
- at higher ph, a pro-peptide is blocking the active site
- at lower ph, autoactivtion happen and the site is exposed
regulation of digestion in the small intestine
- acid chyme passes to duodenum
- mucosal cells release of secretin and CCK into the blood
- gall bladder contracts and pancreas releases juices
what does the pancreas secrete
- bicarb
- inactive zymogens (these are activated by enzymes from the duodenum)
trypsinogen
- activated by enteropeptidase which starts off the process of digestion. made into trypsin
- trypsin acts on trypsinogen to turn it into trypsin
- activates chymotrypsinogen, proelastase, and procarboxypeptidase
degradation of digestive enzymes
- they degrade themselves as they run out of dietary amino acids to work on
- degradation = production (70g/day)
uninhibited trypsin in pancreatic cells
-leads to pancreatitis
-could be from a mutation
-
carboxypeptidase produces
mostly amino acids
aminopeptidases and dipeptidases produce
amino acids
absorption uptake in and out of cells occurs via
- transporters
- there is a high aa concentration in cells so you must use energy to move amino acids in,
- you can just use facilitated transport to move amino acids out
where does amino acid transport occur
- intestines from the lumen
- refiltered from urine in the kidney for reuse
- across mitochondrial membranes
- solute carrier transporters are a diverse group
characterization of amino acid transporters
- often sodium linked transporters that use energy to pump sodium out of the cell in order to establish a sodium gradient that is used to pump the amino acids in (NA/K ATPase)
- one transporter will carry many aa’s that have similar characteristics
where is the first place amino acids go
-liver via portal vein
defective kidney transport for cystine
- can cause cystinuria
- carrier rate of 1:50
- resorption rate rises
- results in high cystein in urin and it is of limiited solubility so it results in stones
- also high lysine
niacin (VB3)
- pellagra
- hartnip
- made from tryptophan
- deficiency disease, pllagra causes its victims to experience dermatitis, dirrhea, and dementia
- clinical features of hartnup disease are nearly identical to thos of pellagra, although more intermittent and slightly less than pellagra
hartnup disease
- abnormal excretion of tryptophan into the urine and deficient in absorption in the intestine
- patient is characterized by intermittent attacks of dermatitis, diarrhea, and dementia
- tryptophan can be converted into niacin, a precursor to NAD
- affects occur in the brin and skin
cathepsins
- lysosomal proteases
- effective for degrading extracellular proteins
sources for amino acids from protein degradation oustide of dietary proteins
- lysosomal system (cathesins)
- digestive enzyme turnover
- the ubiquitin/proteasome pathway (UPP): major pathway for degradation of intracellular proteins (muscle)
degradation rate of proteins
- varies
- proteins that shouldnt be around for a long time such as cell cycle proteins will degrade more quickly
what happens to proteins that are destine for the ubiquitin pathway
- enzymes E1,2, and 3 add ubiquitin to the target which tags it for degradation
- final product is polyubiquitinated
the proteasome
- present in the cytoplasm
- composed of two regulatory particles and a core particle an
- end product is amino acids
- processing is upregulated when needed
regulatory particle
- selects substrates
- remoives Ub for recycling
- edits wrongly tagged proteins
core particle
-this is where proteins are digested into peptides of 7 to 10 aa’s
ubiquitin signals in the protein sequence and not variable
- N end rule: methionine is the slowest
- PEST sequence
- destruction boxes
ubitquitin signals that are external and variable
- phosphoryltaion
- denaturation/damage
- facilitators/chaperons
HPV E6
- faciliates the degradation of p53
- this protein forma complex with its target and makes it more likely to be ubiquinylated
- this is a viral protein which upregulates the cell cycle by degrading p53, a powerful tumor supressor
- certain forms of the virus are assoicated with cervical cancer
parkinsons
- lewy bodies (protein deposits in the brain)
- causes a loss of neurons, dopamine
- L dopa is the most common treatment
parkin and E6AP
-examples od E3 type ubitquitin ligases that are associated with parkinsons and HPV induced disease
plasma
- this is how proteins are transported in the blood
- alanine and glutamine are in the highest concentration due to the way they are metabolized
free amino acids
levels are low compared to that of polymerized aa’s
-95% is turned over every ten mins
essential amino acids
-must be obtained from the fiet
-if something is too hard to make, we eat it
-
list the essential amino acids
- arg
- val
- phe
- his
- thr
- met
- iso
- lys
- leu
- tryp
- are valuable phor his thriving metabolism in lyfes leunatic tryp
inadequate protein in the diet
- kwashiorkor
- marasmus
- bloated stomachs due to loss of plasma protein and fatty liver
quality sources of protein
- animal proteins is of much higher percentage and is broken down much easier
- animal has complete amino acid sources
- chemical score for animal is high
