Lecture 3 Flashcards
What is a transition state?
The enzyme substrate complexes highest energy state usually lasting several picoseconds
Provide some evidence for transition states existence
Transition state analogues are good inhibitors in adenylate kinase
Catalytic antibidies
How does tamiflu work?
It targets salidase which acts as a pathogenic factor in microbial infections. Tamiflu is a transition state inhibitor of this enzyme
How do you make catalytic antibodies?
- Protein of interest is injected into the live host
- Blood sample taken
- Antibody forming cells
- Form hybridomas
- Hybridomas are screened for protein-specific antibody production
- Protein specific monoclonal antibodies isolated
For the antigen a transition state mimic is used
What is the catalytic triad in chymotrypsin?
Ser 195
Asp 102
His 57
What is the oxyanion hole’s function in chymotrypsin?
Stabilises the transition state
How does cyanide work?
It is an irreversible inhibitor of cytochrome c oxidase thus blocking cellular respiration
Which type of enzyme inhibitor can be reversed by dialysis?
Reversible inhibitors
What is strychinine?
A non-competitive glycine receptor inhibitor
How do non-competitive inhibitors work?
They do not affect substrate binding they reduce catalysis itself
Why is hisitidine commonly found in active sites?
It has a pKA of about 6 therefore can be used as an acid or a base at neutral pH
What are serpins?
A form of regulation of serine proteases. They have bait which the proteases grab, the serpin then folds and crushes the protease. Each serpin can only ever degrade one protease due to energy requirements
How was the mechanism of chymotrypsin deduced?
By using: Covalent modification Steady state kinetics Transient state kinetics x-ray crystallography Nmr spectroscopy Site directed mutagenesis
What type of residues was the active site of chymotrypsin found to like?
Bulky hydrophobic
What type of kinetics does chymotrypsin follow?
Transient state kinetics
What is an intermediate?
An enzyme substrate complex formed for a few ms
