Lecture 6 & 7 Flashcards
What are four properties of enzymes?
Specific
Catalytic power (fast)
Efficient
Regulated
What is specificity?
Ability of the enzyme to specifically recognise the proper substrate (reactant)
* Enzyme-substrate recognition and specificity is based on structural complementarity
▪ 3-D fit
What is the active site?
The active site, is a three-dimensional pocket, located in
a small enzyme region (~10–20%), which is composed of:
- substrate binding site
- catalytic site
What happens in the substrate binding site?
- amino acid side chains interact with the the substrate
- through H-bonds and other electrostatic interactions
- to Orientate the substrate within the active site
What happens in the catalytic site?
Amino acids that catalyse the reaction
What is catalytic power?
An enzyme’s ability to speed up the rate of reaction between 10 to the 6 or 10 to the 7x faster
What are the three reasons enzymes are efficient?
- Not altered or
consumed during
or after the reaction
*They are reusable
- They are active at very low concentrations
What factors affect enzyme function?
-Temperature
-ionic conditions
-pH
-Substrate concentration
- Presence of inhibitors
Break down enzyme activity due to temperature
- enzymes have a high optimum temperature (37 in humans)
- lower activity at lower temperature
- will begin to lose activity at high temperatures past optimum = denaturation
What happens during denaturation?
- loss of natural folding of enzyme
- active site and substrate no longer match
-loss of catalytic activity
How does substrate conc affect enzyme activity?
At a constant conc of enzyme, an increase in substrate conc will increase the reaction rate until enzyme becomes saturated
=VMAX
What is Km?
the concentration of substrate at
which the reaction rate is half-maximal
What is the relationship between Km and enzyme binding?
- the higher the Km = the weaker the bonding
- the lower the Km = the stronger the bonding
What is a co-factor?
An additional non-protein reactive group that are essential for activity
What are the two types of co-factors?
essential ions and co-enzymes
(Cosubstrates & prosthetics)
What does a co-substrate entail?
Weakly/temporarily bound to an
enzyme
* Consumed and transformed during
the reaction and dissociate from the
active site (regenerated in another enzymic
reaction and recycled)
What do prosthetic groups entail?
- Tightly or permanently bound to the enzyme
- Are not consumed or altered during reaction
What is a holoenzyme?
A complete catalytically active enzyme together with its co-factor
What is an apoenzyme?
the protein part of the enzyme without its co-factor (not active)
What type of reactions are Oxidoreductases involved in?
Oxidation & Reduction (REDOX) reactions
What are transferases involved in?
- Functional group transfer reactions
- Includes kinases
What are hydrolyses involved in?
- Cleavage of chemical bonds through the addition of
water molecules (proteases, phosphatases, etc)
What are lysases involved in?
- Breaking of chemical bonds within a molecule,
without the involvement of water
What are isomerases involved in?
- Conversion of one isomer into another one
What are ligases involved in?
- Joining of two molecules
What are translocases involved in?
- Movement of molecules or ions across membranes
How much ATP does the oxidation of NADH yield?
2.5 ATP
How much ATP does the oxidation of FADH2 yield?
1.5 ATP
