And so we have to have some type of divalent metal atom. Divalent simply means it has a charge of positive two. So to demonstrate why this is so, let's suppose we have the ATP molecule as our substrate. So this is the ATP. So we have our adenine base, the sugar component, and the triphosphate group. And so the reason we need that magnesium or the manganese, the reason we need a divulge positive metal ion is because the positive metal ion will interact with the negative charges on the oxygen molecule on the oxygen atoms of the triphosphate.