Protein tyrosine phosphatase CD45 as a molecular biosensor of hydrogen peroxide generation in cell culture media

► Novel method of assessing oxidative stress level in biological fluids was designed. ► Protein tyrosine phosphatase CD45 as a biosensor of hydrogen peroxide generation. ► Cell culture media (especially RPMI 1640) reversibly inactivated phosphatase CD45. ► The media-caused inhibition of PTP activity is mediated by hydrogen peroxide. ► The inactivation of CD45 by cell culture media is light-dependent.