Dexfosfoserine (Phosphoserine, L-Serine-O-Phosphate, O-Phosphoserine), the most abundant phosphoamino acid in the eukaryotic phosphoproteome, is not encoded in the genetic code but synthesized posttranslationally. Dexfosfoserine is an agonist of the group III metabotropic glutamate receptors. This endogenous compound inhibits neural stem cells proliferation and promotes survival of nascent neurons thus it has potential therapeutic value in addition to its basic utility as a probe for dissecting molecular mechanisms underlying neurogenesis.