Which one is an essential mineral, not constituent of any enzyme but stimulates the activity of many enzymes?

K is an essential mineral, not a constituent of any enzyme but stimulates the activity of many enzymes.
Potassium is associated with the movement of water, nutrients and carbohydrates in plant tissue. It's involved with enzyme activation within the plant, which affects protein, starch and adenosine triphosphate (ATP) production. The production of ATP can regulate the rate of photosynthesis.