Assaying Arabidopsis lipase activity

A low lipase activity from a crude extract of Arabidopsis seedlings was ass ayed using three sensitive methods (radiolabelled triacylglycerols, commerc ial resorufin ester and triacylglycerols containing the naturally fluoresce nt parinaric acid as substrates). The specific activity of the extract was found to be similar using the three methods. However, the plant lipase acti vity measured using the radioactivity and the fluorescence assays could be abolished by heating the extract, contrary to the apparent activity measure d using the commercial colorimetric assay. Unlike the radioactivity assay,t he fluorescence assay can be monitored continuously. The parinaric acid-bas ed method is therefore the only one to provide a sensitive, specific and co ntinuous assay.