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  1. Michaelis-Menten constant is defined as the substrate concentration (expressed in moles/litre) to produce half-maximum velocity in an enzyme catalyzed  reaction.
  2. It is denoted by the symbol Km.
  3. It indicates that 50% (half) of the enzyme molecules are bound to the substrate molecules when the substrate concentration equals to the Km value.
  4. Km=1/2 Vmax.
  5. Km value varies from substrate to substrate because different enzymes differ in their affinities towards different substrates.
  6. Km value is constant and a characteristic feature of a particular enzyme.
  7. It is an indicative of the degree of strength of the Enzyme-Substrate (ES) complex.
  8. A lower Km value indicates strong affinity between enzyme and substrate, whereas a high Km value reflects weak affinity between them.
  9. The Km values are in the range of 10-5 to 10-2 moles.
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