text: Many phosphatases are promiscuous with respect to substrate type, or can evolve quickly to change substrate. An alternative structural classification notes that 20 distinct protein folds have phosphatase activity, and 10 of these contain protein phosphatases.
  * The CC1 fold is the most common, and includes tyrosine-specific (PTP), dual-specific (DSP) and even lipid-specific (PTEN) families.
  * The major serine/threonine-specific folds are PPM (PP2C) and PPPL (PPP).
  * The only known histidine phosphatases is in the PHP fold.
  * Other folds encode phosphatases that act on various combination of pSer, pThr, pTyr, and non-protein substrates (CC2, CC3, HAD, HP, AP, RTR1).