CMT4B1, or Myotubularin related protein 2, is a human gene encoded by MTMR2. It may also be known as: Myotubularin-related protein 2; phosphatidylinositol-3-phosphatase; phosphoinositide-3-phosphatase; CMT4B. The encoded protein is an enzyme with an amino acid length of 643 and a mass of 73.4 kDa. CMT4B1 is a member of the Protein-tyrosine phosphatase family, Non-receptor class myotubularin subfamily. Homologs of this gene exist in other organisms, including: Mouse, Rat, Zebrafish, Frog, Chicken.