proPO system of Allogamus auricollis (Insecta): Effects of various compounds on phenoloxidase activity

The phenoloxidase activity in the hemolymph cell-free fraction from Allogamus auricollis was studied in the presence of Escherichia coli lipopolysaccharides and Saccharomyces cerevisiae β-1,3-glucans. The proPO system seems to be strongly activated by lipopolysaccharides (LPS). The basic activation observed in this model appears not to be affected by the use of protease inhibitors (α2 macroglobulin, soybean trypsin inhibitor), and, in addition, the LPS-activated proPO system is not inhibited by their presence. Calcium ions at high concentrations inhibit the phenoloxidase activity, and EDTA chelation strongly enhances dopachrome formation. Analytical polyacrylamide gel electrophoresis (PAGE) of the hemolymph cell-free fraction showed two main components, with a molecular mass of 76 and 80 kDa. After electro-elution from a native PAGE of L-dihydroxy-phenylalanine positive bands, the analytical SDS-PAGE again showed the same two major bands.