Hyaluronidases are only active in acidic environments. HYAL2 can interact with the Na+-H+ exchanger (SLC9A1, NHE1) which can create an acidic microenvironment in the caveolae. Extracellular Na+ ions are exchanged for protons which creates the acidic conditions required for the activity of HYAL2 (Bourguignon et al. 2004). The interaction of calcineurin homologous protein 1 (CHP1) with SLC9A1 is essential for the maintenance of, or increasing, the pH sensitivity of SLC9A1 thus CHP1 can regulate SLC9A1 activity (Lin & Barber 1996, Pang et al. 2004, Mishima et al. 2007). CHP1 depletion in Xenopus oocytes results in a dramatic reduction (>90%) in the Na+-H+ exchange activity of SLC9A1 (Pang et al. 2001).