Spacing

        Some enzymes can be covalently bound to a polymer while still retaining activity. Assume in the next figure that the CH2 groups have somehow been activated to bind with enzymes. The black bar is the polymer (backbone), the red blob (should be much larger) is the enzyme, and the yellow oval is its active site.

Take a look at an animation, then come back to here.

Some serious faults in the sketch:

  1. The backbone is some polymer, not just some pipe or rod as shown.
  2. Binding with a CH2 group is unlikely, and there is probably some other group such as benzene ring.
  3. Enzymes are hundreds of times bigger than CH2 groups.
  4. Many enzymes are ellipsoidal, but don't line up uniformly. The attachment sites would vary.
  5. The enzymes point out at various angles in 3 dimensions.
        For an enzyme only one CH2 away, it would be very difficult for a substrate to find the active site. The backbone interferes sterically. With more CH2 (or other spacing groups), the enzyme can whip around and twist so that the active site is much more accessible. Usually, spacers that provide as much distance as six CH2 groups are enough.


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