What is covalent catalysis?
The active site contains a nucleophile that is briefly covalently modified.
This modification enhances the reaction rate by forming a transient intermediate.
What is general acid-base catalysis?
A molecule other than water donates or accepts a proton.
This process helps stabilize charged transition states.
How do metal ions function in catalysis?
Metal ions function in a number of ways including serving as an electrophilic catalyst.
They can also stabilize negative charges and facilitate electron transfer.
What is catalysis by approximation and orientation?
The enzyme brings two substrates together in an orientation that facilitates catalysis.
This increases the likelihood of productive collisions between substrates.
Fill in the blank: In covalent catalysis, the active site contains a _______.
[nucleophile]
True or False: General acid-base catalysis involves water as the proton donor.
False
It specifically involves a molecule other than water.
List the common catalytic strategies.
- Covalent catalysis
- General acid-base catalysis
- Metal ion catalysis
- Catalysis by approximation and orientation
What is acid-base catalysis?
A process where acids or bases accelerate a chemical reaction.
What does ‘uncatalyzed’ refer to?
A reaction that occurs without the assistance of a catalyst.
What is acid catalysis?
A type of catalysis that involves the addition of an acid to speed up a reaction.
What is base catalysis?
A type of catalysis that involves the addition of a base to speed up a reaction.
What is ‘specific’ acid-base catalysis?
Involves H + or OH - that diffuses into the catalytic center.
What is ‘general’ acid-base catalysis?
Involves other acids and bases that facilitate transfer of H + in the transition state.
What is the typical pH range in which most enzymes are active?
5-9
How does pH affect the binding of substrate to enzyme?
It can influence the binding of substrate to enzyme.
What role does pH play in the ionization states of amino acids?
It affects the ionization states of the amino acids involved at the catalytic site.
How does pH impact the ionization states of the substrate?
It influences the ionization states of the substrate.
What effect does pH have on protein structure?
It can cause variation in protein structure.
What is required for enzymatic activity in certain amino acid residues?
Specific ionization state
The ionization state affects the functionality of amino acids in enzymes.
What are the pKa values for Asp or Glu?
~ 4
The pKa value indicates the pH at which half of the species is deprotonated.
What is the pKa value range for His?
~ 6 or 10
Histidine can be protonated or deprotonated depending on the pH, affecting its role in enzymes.
How does the microenvironment affect amino acid residues?
Changes the pKa value
The local environment can significantly influence the ionization state of amino acids.
What is the optimal temperature range for most enzymes?
Around 37 C
This temperature is typical for human enzymes, which function best at body temperature.
What happens to enzyme kinetics when temperatures are too cold?
Slows down kinetics
Lower temperatures can reduce the molecular movement, leading to decreased reaction rates.
