Peroxidase takes place when the enzyme-substrate complex forms

Peroxidase catalyzes the decomposition
of hydrogen peroxide by providing an alternative reaction pathway with a lower
activation energy without being neither destroyed or altered in the process. The
reaction takes place when the enzyme-substrate complex forms at the active site
and the enzyme converts the substrate into the product(s). Based on this model,
the rate at which the product can be produced depends on the amount of enzyme
and substrate that are present during the reaction. If the peroxidase
concentration is kept constant and the concentration of substrate is increased,
the rate of the reaction will increase rapidly until half of the enzyme becomes
saturated with substrate. At this point, the rate of the reaction will not
increase as rapidly and eventually the rate of the reaction will approach a
constant rate even when the substrate concentration is increased, otherwise
known as the maximum velocity (Vmax).

When the reaction rate ceases to increase, the maximum velocity for the
reaction has been reached. The substrate concentration that coincides with half
of the maximum velocity (½Vmax)
is known as the Michealis-Menten constant (Km).

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At this concentration, half of the enzyme molecules in solution are bound to
the substrate.

 

Figure 1: The derivation of Vmax and Km from
a reaction velocity-substrate concentration graph

      Inhibitors are chemical substances that bind to an enzyme and decrease
its activity. Whereas a competitive inhibitor binds to the active site
preventing the substrate from binding and thereby reducing the enzyme molecules
available to bind, non-competitive inhibitors bind to a place other than the
active site (the allosteric site) preventing the enzyme from catalyzing the
reaction and thereby reducing the number of enzymes that can successfully carry
out the reaction.  Competitive and
non-competitive inhibition are xxx. Competitive inhibition does not alter the Vmax as there is still a
substrate concentration where full enzyme activity can be achieved. However, it
takes a higher substrate concentration to reach this rate therefore increasing Km. Non-competitive inhibition
decreases the Vmax because
the enzymes have been decommissioned by the inhibitor and are unviable.

However, the value of Km
is not altered because the uninhibited enzymes are still functional. By finding
the values of Vmax and Km of turnip peroxidase
without and with Al3+ ions, I can therefore determine whether Al3+
ions inhibit the activity of turnip peroxidase and whether the ions
inhibit  competitively or
non-competitively.