Phosphorylation is one of the most important protein post-translation modifications. The phosphorylation of threonine is the addition of a phosphoryl group to its polar side chains group through the action of a threonine kinase. Threonine phosphate (also known as phosphothreonine) can be detected in the urine of human. Besides, was revealed the age dependence excretion of phosphothreonine acid in normal subjects.