Production of enzymes in the cell

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Production of enzymes in the cell
Enzymes can be produced at constant levels in the
cell (constitutive enzymes) OR
Their production can be regulated in response to
substrate( induced enzymes) or product
concentrations (feedback mechanisms).
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• Constitutive enzymes always present, always
  produced in equal amounts or at equal rates,
  regardless of amount of substrate
• enzymes involved in glucose metabolism
• Regulated enzymes not constantly present
  production is turned on (induced) or turned off
  (repressed) in response to changes in
  concentration of the substrate

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Enzyme Inhibitors

• An effective way to control the growth of
  bacteria is to control their enzymes
• Certain poisons such as cyanide, arsenic and
  mercury combine with enzymes and inhibit their
  activity
• Enzyme inhibitors can be classed as
• Competitive inhibitors
• Noncompetitive inhibitors

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Competitive inhibitors

• Fill the active site and compete with substrate
• Similar in shape and chemical structure to the
  substrate
• Does not undergo any reaction to form products
• May bind reversibly or irreversibly.

e.g., Inhibition of folic acid synthesis by
sulfanilamide
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Noncompetitive inhibitors

• Interact with a site other than the active site
  (allosteric or regulatory site)
• Binding of the inhibitor causes a change in the
  shape of the active site, making it nonfunctional
  (allosteric inhibition)
• May bind reversibly or irreversibly

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Enzyme Repression

• The end-product of the reaction signals back to
  the DNA to turn off expression of the gene
• Prevents the cell from wasting energy

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The Cells Energy Machine