describe the mechanism of absorption of dietary protein?
- gastric and pancreatic proteases with intestinal brush border peptidases degrade protein
- constituents are co-transported into cells where cystolic degradation of di/tripeptides further degrades them into amino acids
what is primary gastric protease?
pepsin
where is pepsin released from?
- chief cells in stomach secrete pepsinogen
- pepsinogen is converted to pepsin
what does pancreatic proteases include?
- trypsin
- carboxypeptidases
how does apical cellular uptake utilise?
- hydrogen recycling
- pumping out co-transported hydrogen through Na/H-counter transporters
describe mechanism of absorption of nuclei acids?
- nuclei acids are digested in gut
- absorbed in small intestine
- pancreatic DNAase and RNAase degrade nucleic acids into constituents nucleotides and nucleosides
what facilitate cellular uptake of nucleosides and nucleotides?
- sodium and hydrogen ions coupled accumulative transporters in intestine
what are the defects in protein digestion?
- trypsin deficiency
- enterokinase deficiency
- prolidase deficiency
what does trypsin deficiency cause?
- inactivation of pancreatic proteases and marked mal-absorption with severe diarrhoea and oedema
what does enterokinase deficiency cause?
- cause trypsin deficiency
- because enterokinase activates trypsin
what is prolidase?
- cytosolic exopeptidase
what does defects in amino acid absorption include?
- hartnup disease
- cystinuria
- lysinuric protein intolerance
what does hartnup disease cause?
- defect in apical amino acid uptake
- phenylalanine is lost in urine
what does cystinuria cause?
- defect in apical amino acid uptake
- cysteine and cationic amino acids lost in urine
what does lysinuric protein intolerance cause?
- defect in basolateral amino acid transport
- vomiting
- diarrhoea
- hyperammonaemia
- skeletal
- immunological abnormalities
which two disease does not involve in malnutrition of associated amino acids and why?
- hartnup and cystinuria disease
- di/tripeptide absorption can provide for them
