Page 73 - Medicinal Plants 02-06-06-101_First year_PharmD (1)

- At very high substrate concentration, the active sites of all the
enzymes molecules are saturated with substrate and the velocity
reaches maximum and remains constant.

In the living plant tissue, enzymes and substrates occur together but
are separated by compartmentalization. After collecting the plant, the cell
dies and the cell walls become more permeable and allow freely the transfer
of fluids and mixing between enzymes and substrates.
e.g.1: Myrosin enzyme present in mustard seeds hydrolyse sinigrin
glycoside when the seeds are crushed and moistened. However, when the
water content of the tissues is below 5% enzymatic reaction are negligible.
e.g.2: Peroxidase is present in fresh opium and causes the loss of up to 50%
of morphine content, this is prevented by heating opium to 70oC.

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