Diagnostic Enzymology
LO:
• Fundamental principles of enzymology; catalysis, rates, energy states, enzyme hypotheses,
active sites, inhibitors
• Define specificity, sensitivity & selectivity
• Units involved in measuring enzyme activity; IU/L, katal, the use of enzyme activity vs.
enzyme mass determinations
• Sampling/diagnostic considerations; errors/impurities in sampling, reference ranges,
variations
• Knowledge of commonly assayed diagnostic enzymes; transaminases, creatine kinases (CK),
lactate dehydrogenase (LDH), amylase, alkaline phosphatase (ALP), gammaGT
• Specific uses of isoenzymes in disease diagnosis; LDH, CK & ALP, be able to discuss their
profiles in a human disorder
Enzyme fundamentals
What are enzymes? Proteins which catalyse biological reactions
Enzyme Properties?
Highly specific
Unchanged after reaction
Can accelerate reactions >106 fold
Can catalyse the reaction multiple times
Cannot alter reaction equilibria
Conversion of substrate to product:
Enzyme terminologies
Specificity: how restrictive is the choice of substrate by the enzyme
- shape of active site
Sensitivity: enzyme ability to catalyse multiple substrate molecules
- measurable
- level of activity
Selectivity: is a property of the substrate
- degree to which substrate can be catalysed by different enzymes
Active site: Region of enzyme where reactions occur; small portion of enzyme
- Creates a microenvironment, e.g often excludes water
Specificity: Complementarity between enzyme and substrate
, - Emil Fischer (1890) – Lock and Key
- Dan Koshland (1958) – Induced fit
- Enzyme reshaped by substrate binding
Lock & key vs. induced fit
The key point is the transition state
The lock and key idea originated ~1890, it was replaced by the induced fit model.
We have an induced fit model of enzyme activity whereby we have a conformational change in
enzyme morphology to bring about chemical reaction bringing reacting species in contact with each
other.
Induced fit.
ADH = alcohol dehydrogenase
ALDH = aldehyde dehydrogenase
Induced conformational changes: hexokinase
LO:
• Fundamental principles of enzymology; catalysis, rates, energy states, enzyme hypotheses,
active sites, inhibitors
• Define specificity, sensitivity & selectivity
• Units involved in measuring enzyme activity; IU/L, katal, the use of enzyme activity vs.
enzyme mass determinations
• Sampling/diagnostic considerations; errors/impurities in sampling, reference ranges,
variations
• Knowledge of commonly assayed diagnostic enzymes; transaminases, creatine kinases (CK),
lactate dehydrogenase (LDH), amylase, alkaline phosphatase (ALP), gammaGT
• Specific uses of isoenzymes in disease diagnosis; LDH, CK & ALP, be able to discuss their
profiles in a human disorder
Enzyme fundamentals
What are enzymes? Proteins which catalyse biological reactions
Enzyme Properties?
Highly specific
Unchanged after reaction
Can accelerate reactions >106 fold
Can catalyse the reaction multiple times
Cannot alter reaction equilibria
Conversion of substrate to product:
Enzyme terminologies
Specificity: how restrictive is the choice of substrate by the enzyme
- shape of active site
Sensitivity: enzyme ability to catalyse multiple substrate molecules
- measurable
- level of activity
Selectivity: is a property of the substrate
- degree to which substrate can be catalysed by different enzymes
Active site: Region of enzyme where reactions occur; small portion of enzyme
- Creates a microenvironment, e.g often excludes water
Specificity: Complementarity between enzyme and substrate
, - Emil Fischer (1890) – Lock and Key
- Dan Koshland (1958) – Induced fit
- Enzyme reshaped by substrate binding
Lock & key vs. induced fit
The key point is the transition state
The lock and key idea originated ~1890, it was replaced by the induced fit model.
We have an induced fit model of enzyme activity whereby we have a conformational change in
enzyme morphology to bring about chemical reaction bringing reacting species in contact with each
other.
Induced fit.
ADH = alcohol dehydrogenase
ALDH = aldehyde dehydrogenase
Induced conformational changes: hexokinase
