This key glycolysis intermediate (a hexose diphosphate) was discovered by Arthur Harden and William Young in 1905. In the third step of glycolysis, fructose 6-phosphate and ATP are converted to fructose 1,6-bisphosphate and ADP with the aid of phosphofructokinase. In step 4, fructose 1,6 bisphosphate (with the aid of aldolase) is cleaved into duhydroxyacetone phosphate and glyceraldehyde 3-phosphate.