SFP8: Substrate Binding Of Enzymes Flashcards
What is the active site of an enzyme
The region of an enzyme where substrates bind and catalysis occurs
What is Pauling 1946 model of substrate binding
Concept of flexible active site
What does the rest of an enzyme do away from the active site?
Maintain structural role
Can favourable binding energy offset energetically unfavourable chemical steps
Yes-
Chemical catalysis is not enough to explain rate enhancement of majority of enzymes
What is binding energy?
Free energy released upon the interaction of a complementary enzyme and substrate
What are serine proteases?
A family of proteolytic enzymes
Catalyse hydrolysis of peptide bond
When treated with organophosphate, does the serine protease lose its activity reversibly or irreversibly?
Irreversible
look over serine proteases mechanism
Mechanism and specificity
What does an endopeptidase do?
Attack interior peptide bonds
What are the three regions of an active site?
1) activated serine
2) oxyanion hole
3) large hydrophobic pocket (chymotrypsin)
What is chemotrypsin activated by?
Specific cleavage of a single peptide bond
Describe stages of activation of inactive chymotrypsin produced by the pancreas
Activated when the peptide bond between Arg-15 and Ile-16 is cleaved by trypsin
Results in pi-chymotrypsin cleaves other pi-chymotrypsin molecules to form an alpha-chymotrypsin
The 3 peptide chains produced are held together by two interaction disulphide bonds
Where do restriction enzymes cleave DNA?
At highly specific positions
What class of endonucleases is most commonly referred to?
Type II
How do restriction enzymes hydrolyse phosphodiesterase bond?
By a one step mechanism (unlike serine proteases)
No covalently bound intermediate
Mechanism similar to that used by metaloproteases
Require Mg2+ for activity
Metal ion stabilises the developing negative charge during hydrolysis
