In 1833 French chemist Anselme Payen was the first to discover an enzyme, diastase. The commonly used -ase suffix for naming enzymes was derived from the name diastase. French chemist Anselme Payen was the first to discover an enzyme, diastase, in 1833. At first, the hot water dissolves the sugars (maltose) and enzymes (diastase) in the grist. Fungi, on the other hand, stains darkly with PAS even after treatment by diastase. Payen discovered the first enzyme, diastase, in 1833. Specifically, the grain enzyme diastase begins to convert starch in the grain to maltose. For example, glycogen is darkly stained by PAS but can be dissolved by diastase. When PAS and diastase are used together, a light pink color replaces the deep magenta. The xanthoma cells contain periodic acid Schiff positive, diastase resistant granules. PAS diastase staining varies from negative to focal or granular positivity to strongly positive. When used as a pharmaceutical drug, diastase has the ATC code .