10 protein absorption Flashcards
What are the 4 major pathways of protein absorption?
luminal proteases hydrolyse into amino acids, which are then absorbed
luminal proteases do a bit, finished by brush border enzymes
oligopeptides absorbed by enterocytes (some amino aicds yielded by cell)
same but straight into blood
What Is trypsin activated from, and by what?
trypsinogen by enterokinase
What king of products do endopeptidasses and exopeptidases yield?
endopeptidases - oligopeptides
exopeptidases - amino acids
What other enzymes does trypsin activate?
chymotrypsinogen into chymotrypsin
proelastase into elastase
procarboxypeptase A into carboxypeptase A
procarboxypeptase B into carboxypeptase B
How can exopeptidases yield amino acids?
they can be either C or N terminal peptidases to release terminal aa’s
What accompanies oligopeptides into the cell?
H+, decreasing fasting pH
What units make it into the cell, what makes them all the same?
tripeptides, dipeptides, and amino acids, and tripeptidases and dipeptidases
What transporter facilitates luminal uptake of oligopeptides?
PepT1
What are the 4 groups of amino acid considered in amino acid absorption?
glycine and proline
cationic amino acids
neutral amino acids
anionic amino acids
How are glycine and proline transported?
Na+ dependent, IMINO transporter
What is significant about sodium?
We want to be driving Na+ into the cell too, so the IMINO and EAAT3 transporters do this. b0+ and B0 do this in conjunction
How do B0 and b0+ get sodium and cations and neutral amino acids into the cell?
b0+ transports cationic amino acids in, neutral aa’s out. this allows B0 to transport neutral aa’s in as well as sodium.
How is the sodium gradient maintained in the cell?
Na/K atp hydrolase
What is Hartnup disease?
autosomal recessive
limited B0, but neutral aa’ can still be absorbed in oligopeptides
In what 2 ways can the adult intestine absorb polypeptides?
enterocyte phagocytosis
Peyer’s patches, microvilli package protein in clathrin vesicles
