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Abstract
Solar ultraviolet water disinfection (SODIS) is a process in which contaminated water is exposed to sunlight in plastic bottles to create reactive oxygen species (ROS) including H O to eliminate bacteria and other biological 2 2 pathogens. However, the efficacy of this treatment is reduced by the presence of the enzyme catalase in bacteria which breaks down hydrogen peroxide (H O ) and the presence of phthalate, a chemical commonly found in many 2 2 plastics, which is believed to act as a UV filter by absorbing the UV-A wavelengths of sunlight. In this study, we asked whether the presence of phthalate protects the activity of catalase exposed to UV-A radiation. To measure catalase activity kinetically we used two assays: the H O spectroscopy microassay and the Triton X-100 foam 2 2 production assay. K and V were determined to quantitatively characterize the effects on enzyme activity. m max Phthalate was found not act as a UV-A filter to protect catalase from UV-A irradiation. However, phthalate is capable of protecting both the substrate-binding and catalytic ability of catalase at concentrations of 0.4 μg/L by other means yet to be identified. At higher concentrations of 50,000 μg/L, phthalate becomes an uncompetitive inhibitor of catalase that decreases catalytic activity by binding to the enzyme-substrate complex.