Complex sentence: PFK1 is activated by high concentration of AMP, but the most potent activator is fructose 2,6-bisphosphate, which is also produced from fructose-6-phosphate by PFK2.
Split into simpler sentences: PFK1 is activated by high concentration of AMP. It is also activated by high-levels of AMP but the most potent activator is fructose 2,6-bisphosphate, which is also produced from fructose-6-phosphate by PFK2.