The basic reason why unripe fruits have defensive chemicals is that they need to protect the seeds that are not ready to germinate. On the other hand, the seeds of the ripe fruits are ready to germinate and so they need to get spread with the help of animals and birds and so there are no defensive chemicals. These seeds spread to different places and the soils help them to germinate under suitable conditions.
Because the enzyme has changed its shape it has become unreversably denatured the active site does not match the substrate thefore their will be no reaction
