Phosphomonesterase is an enzyme that hydrolyses phosphoric acid esters bearing a single ester linkage, releasing free phosphate and the alcohol component. The group includes the acid and alkaline phosphatases, workhorse enzymes of digestion and metabolism that liberate phosphate from dietary compounds so it can be absorbed and used. In food science, phosphatase activity is famously exploited as a pasteurisation indicator: alkaline phosphatase in raw milk is destroyed by proper heat treatment, so its absence in tested milk confirms adequate pasteurisation, a test used worldwide for nearly a century. Phytase, a specialised phosphomonoesterase, breaks down phytic acid in grains and legumes, improving mineral bioavailability, and is added to animal feeds and bread doughs for that purpose. The enzymes quietly govern phosphate’s journey from food to bone.