Endosome acidification Authored: Bevan, AP, 2003-07-31 08:01:55 Edited: Jassal, B, 2010-08-09 Pubmed3061785 Pubmed8682206 Pubmed9793760 Reactome Database ID Release 4374723 Reactome, http://www.reactome.org ReactomeREACT_2002 Reviewed: He, L, 2010-08-09 The effect of the proton pump is to allow entry of [H+] ions into the lumen of the endosome. The net effect of this is to lower the pH of the lumen from pH 7.4 (the pH at the plasma membrane) to pH 6.0 (documented with studies using FITC-labeled insulin - a pH dependent fluorescence marker).