Enzyme inhibitors & Immobilised enzymes Flashcards
Inhibitors
Any substance that slows down or stops an enzyme catalysed reaction is an inhibitor.
There are 2 types:
-Competitive
-Non-competitive
Competitive Inhibitors
- They have a similar shape to the substrate and it can fit into the active site. This blocks the active site and prevents the enzyme substrate complex forming. This results in a slower rate of reaction because fewer active sites are available to catalyse the reaction.
- These are reversible
Non-Competitive inhibitors
-A non-competitive inhibitor is a different shape to the substrate and binds to the enzyme at a site other than the active site known as the allosteric site.
The binding causes the enzyme’s tertiary structure to change, which changes the shape of the active site so the substrate can no longer fit and no ES complexes are formed.
-Some are reversible and some are non-reversible
Uses
- Enzyme inhibitors occur naturally and are involved in the control of metabolism.
- For example, enzymes in a metabolic pathways can be inhibited by the products.
- This type of negative feedback shows flux through a pathway when the products begin to build up and is an important way to maintain homeostasis in a cell.
- Cancer Drugs
- Painkillers
- Poisons
The effect of cyanide
- Cyanide is a strong poison. It works as a respiratory inhibitor. The enzyme cytochrome oxidase catalyses the reaction.
- If the enzyme is inhibited, ATP is not produced and the organism quickly dies
- Heavy metals such as lead, mercury, copper or silver are poisonous. This is because ions of these metals are non-competitive inhibitors for several enzymes
Immobilised enzymes
- Immobilised enzymes are attached, fixed or bound to small beads made of alignate (cellulose microfibrils)
- attached to a solid support
- Immobilised enzymes are widely used in industry because it allows the reaction to flow continuously and the product will not be contaminated with the enzyme so will not need to be purified
- Saves time and money - more profit
Advantages of Immobilised enzymes
- Enzymes are kept separate from the products so purification costs are low
- Enzymes immediately available for re-use, no need for complicated extraction process
- Immobilised enzymes are more stable because the immobilising matrix protects the molecules (eg from temperature changes or pH changes)
- Faster, or efficiently process
- enzyme easily removed/added
- more controlled or can control rate
- more than one enzyme can be used
Negatives of Immobilised enzymes
- Immobilising enzymes is more expensive
- Immobilised enzymes may give slower reaction rates as molecules do not mix freely with substrate molecules
- Substrate has to diffuse into bead structures or through mesh
- Contamination is more difficult to deal with
Uses of immobilised enzymes
1)Production of lactose free milk for people who are lactose tolerant
Lactose->Glucose+Galactose
2)High Fructose corn syrup
Glucose (corn syrup) -Glucose Isomerase-> Fructose
-Biggest industrial use of immobilised enzymes
-The enzyme glucose isomerase is immobilised, and converts the glucose in the corn syrup to fructose, which is sweeter
Uses of immobilised enzymes - Biosensors
- Enzyme detects the substrate
- Substrate is converted in product
- Transduction - chemical signal into electrical impulses
- The current produced can be read on the scale
- The products causes a potential difference which is measured by an electrode
How are immobilised enzymes used in biosensors?
The specificity of enzymes means that they can be used to test for a unique substance, which is exactly what a biosensor does
Advantages of biosensors
- Specific
- Accurate
- Detect or sensitive to low concentrations
- Quantitative result obtained
- Rapid/Quick
Glucose test strips
-Biosensors are used by diabetics to measure the amount of glucose in their blood. They have an immobilise enzyme (glucose oxidase) bind to the machine which gives a digital reading. Diabetics test their blood glucose levels using biosensors.
