The myotubularin family is a large eukaryotic group within the 
tyrosine/dual-specificity phosphatase super-family (PTP/DSP). Among the 14 human 
members, three are mutated in genetic diseases: myotubular myopathy and two 
forms of Charcot-Marie-Tooth neuropathy. We present an analysis of the 
myotubularin family in sequenced genomes. The myotubularin family encompasses 
catalytically active and inactive phosphatases, and both classes are well 
conserved from nematode to man. Catalytically active myotubularins 
dephosphorylate phosphatidylinositol 3-phosphate (PtdIns3P) and PtdIns3,5P2, 
leading to the production of PtdIns and PtdIns5P. This activity may be modulated 
by direct interaction with catalytically inactive myotubularins. These 
phosphoinositides are signaling molecules that are notably involved in vacuolar 
transport and membrane trafficking. Myotubularins are thus proposed to be 
implicated in these cellular mechanisms, and recent observations on 
myotubularins homologues in the nematode Caenorhabditis elegans indicate a role 
in endocytosis.