ENZYMES

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ENZYMES

• CHEM 106
• SPRING 2003

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General Characteristics

• Catalytic Efficiency
• - Carbonic Anhydrase
• Specificity
• - Absolute specificity
• - Relative specificity
• - Stereochemical specificity
• Regulation

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Classification
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Definitions
Apoenzyme inactive form of the enzyme Cofactor
non-protein molecule or ion required by an an
enzyme for catalytic activity (weakly
bound) Coenzyme an organic molecule required by
an enzyme for activity Holoenzyme apoenzyme
plus all cofactors or coenzymes necessary for
activity Active Site region of enzyme where the
substrate binds
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Mechanism
Enzyme
Substrate
Enzyme Substrate Complex
Enzyme
Product
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Mechanism
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Enzyme Activity
Enzyme Activity the rate at which an enzyme
catalyzes a reaction Turnover number the number
of molecules of substrate that is acted on by one
enzyme molecule per minute
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Turnover numbers
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Factors Affecting Activity

• Enzyme Concentration
• Substrate Concentration
• Temperature
• pH

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Enzyme Concentration
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Substrate Concentration
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Temperature
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Effect of pH
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Optimum pH
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Enzyme Inhibition
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Irreversible Inhibition
An irreversible inhibitor forms a covalent bond
with a specific functional group of the enzyme.
Cyanide ion it interferes with the operation of
an Fe containing enzyme called cytochrome
oxidase. Hg2 and Pb2 reacts with SH groups
on many enzymes Antibiotics see table
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Irreversible Inhibition
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Reversible Inhibition
Competitive Inhibitors Inhibitor competes for
the active site Noncompetitive Inhibitors Inhibit
or binds to another location other than the
active site causing a changes in activity
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Competitive Inhibitors
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Competitive Inhibitors
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Noncompetitive Inhibitors
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Regulation of Enzyme Activity
Activation of Zymogens Zymogens inactive
precursors of enzymes Allosteric
Regulation Allosteric Enzymes Feedback
Inhibition Genetic Control Enzyme induction
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Activation of Zymogens
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Allosteric Regulation
Allosteric Enzyme an enzyme with quaternary
structure whose activity is changed by the
binding of modulators Modulator a substance
that binds to an enzyme at a location other than
the active site and alters the catalytic
activity. Can be an activator or a
deactivator Activator increases the
activity Deactivator decreases the activity
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Feedback Inhibition
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Medical Applications
Clinical Diagnosis Isoenzymes
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Clinical Diagnosis
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Isoenzymes
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Isoenzymes