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Flashcards in Lecture 3 Deck (16):

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?

1. Protein of interest is injected into the live host
2. Blood sample taken
3. Antibody forming cells
4. Form hybridomas
5. Hybridomas are screened for protein-specific antibody production
6. 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