Type III Na+/Pi cotransport Authored: Jassal, B, 2009-06-23 Edited: Jassal, B, 2009-06-23 Pubmed10516278 Pubmed2078500 Pubmed8302848 Reactome Database ID Release 43427605 Reactome, http://www.reactome.org ReactomeREACT_19410 Reviewed: He, L, 2009-08-24 There are two transporters of this type; The genes SLC20A1 and SLC20A2 encode for PiT1 (phosphate transporter 1) and PiT2 respectively. They both have a broad tissue distribution and may play a general housekeeping role in phosphate transport such as absorbing phosphate from interstitial fluid and in extracellular matrix and cartilage calcification as well as in vascular calcification. These proteins were originally described as retroviral receptors for the gibbin ape leukemia virus receptor 1 (GLVR1, now called PiT1) (O'Hara B et al, 1990) and GLVR2 (now called PiT2) (van Zeijl M et al, 1994). However, they were found to possess Na+-coupled phosphate cotransporter function (Fernandes I et al, 1999). The transport is electrogenic with a stoichiometry of 2:1 (Na+:Pi). has a Stoichiometric coefficient of 2