Factors affecting enzymes activity
Factors affecting enzymes
activity:
- Substrate concentration
- Enzyme concentration
- pH
- Temperature
How enzyme activity measured ?
- Decrease in substrate concentration
- Increase in product concentration
- Reaction velocity is the amount of substrate converted in to product per time
- Increase in substrate concentration leads to increase in the velocity of reaction .
- At Vmax increase in the amount of substrate causes no increase in the velocity of the reaction .
Michaelis constant (Km
) :is the substrate concentration at half maximum velocity
- It measures the enzyme affinity to substrate
- Low Km means high affinity to substrate
- High Km mean low affinity to substrate
Lineweaver-Burk plot
- To calculate the Vmax
- To calculate the Km
- To determine the type of inhibitor
- Increase in the enzyme concentration leads to increase in the velocity of reaction
Optimal pH :
- the pH at which enzyme acts maximally .
- Above or below this pH the rate of reaction will decreased .
- Each enzyme has its own pH.
Temperature
- The reaction velocity increases with the temperature until a peak velocity is reached .
- Further increase in temperature decrease reaction velocity as a result of denaturation.
- Most enzymes are denatured at 55-60 .
Inhibitors of enzymes:
- Competitive Inhibitors
- Non competitive Inhibitors
Enzymes regulation
- Why are enzymes regulated?
The biochemical reactions in
the body found as a pathways. Cells do not need all
activities at one time . So each pathway has its own
regulatory enzyme(s)
Regulation of enzymes:
- Feedback inhibition
- Covalent modification : adding or removal of phosphate
Allosteric enzymes
Have another site in addition
to the active site . The other site binds to
modulators. Modulator may be positive or
negative .
Compartmentalization Enzymes
found in cellular sub-compartments such as lysosomes or mitochondria and are
only active there Control of synthesis and
degradation :
- Constitutive enzymes (continuous synthesis)
- Adaptive enzymes (on demand)
Zymogens : (inactive enzymes) the active site is covered by a peptide mask.
Isozymes : are more than one enzyme catalyze the same reaction.
Clinical importance of isoenzymes:
- diagnosis of some diseases eg:
- LDH1 important in heart disease
(myocardial infarction)
- LDH5 important in liver
diseases
- LDH1 important in heart disease (myocardial infarction)
- LDH5 important in liver diseases
No comments:
Post a Comment