Complex sentence: PBO acts as an insecticide synergist by inhibiting the natural defense mechanisms of the insect, the most important of which is the Mixed Function Oxidase system, (MFOs) also known as the cytochrome P-450 system.
Split into simpler sentences: PBO acts as an insecticide synergist by inhibiting the natural defense mechanisms of the insect. PBO inhibits enzymes present in insects, the most important of which is the Mixed Function Oxidase system, (MFOs) also known as the cytochrome P-450 system.