Lecture 28 - Amino Acids as Fuel Molecules Flashcards
What does protein digestion involve?
Hydrolysis of peptide bonds, performed by several different proteases and peptidases
What do endopeptidases do?
attack (break) peptide bonds within the protein (peptide) polymer
What do exopeptidases do?
attack (break) the last peptide bond near the end of protein (peptide) polymer
What are some examples of Endopeptidases?
Pepsin, Trypsin, Chymotrypsin
What is endopeptidase specificity determined by?
adjacent amino acid side chains in protein substrate
What best describes how endopeptidases work?
Sequential (each round produces smaller peptides)
What are some examples of exopeptidases?
Carboxypeptidase, Aminopeptidase
What is the order in which proteases digest proteins?
- Pepsin
- Trypsin
- Chymotrypsin
- Carboxypeptidases
- Aminopeptidases
Where does a carboxypeptidase cut the peptide?
Near the carboxy-terminal residue
Where does an aminopeptidase cut the peptide?
Near the amino-terminal residue
What do exopeptidases release?
Amino acids, di- and tri- peptides
How are proteases produced?
As zymogens
Why are proteases produced as zymogens?
Need to prevent protease activity before reaching the
gastrointestinal tract
What are zymogen or proenzymes?
Proteases secreted as inactive forms
How are zymogens activated?
by cleavage of peptides from their structure
What is the autolytic activation of pepsinogen?
activation by the low stomach pH
What is the catalytic activation of pepsinogen?
When the activated pepsin interacts with pepsinogen, activating it
How is trypsinogen activated into trypsin?
Membrane-bound enterokinase (enteropeptidase)
How is chymotrypsinogen activated?
By trypsin, and chymotrypsin activating other chymotrypinogens