Purification and characterization of glutathione S-transferases from two syrphid flies ( Syrphus ribesii and Myathropa florae)

Abstract

Glutathione S-transferases (GST) play an important role in the detoxification of many substances including organic pollutants and plant secondary metabolites. We compared the GST of two syrphid species, the aphidophagous Syrphus ribesii and the saprophagous Myathropa florea to assess the relation between feeding type and GST patterns. Differences between the GST of the hoverfly species were observed after purification by affinity chromatography, SDS-PAGE and kinetic studies. While the specific activities of the purified enzymes were different, the purification yields were similar. The variation in specific activities was related to the presence of different isoenzymes in both syrphid species by SDS-PAGE. While two bands of 24 and 32 kDa were observed for M. florea, one more band of 26 kDa was present in S. ribesii. When a range of substrate and glutathione concentrations was tested, differences in K m and V max between the glutathione S-transferases from both hoverfly species were also observed. These results are discussed in terms of adaptations to the feeding habit and the habitat of the two syrphid species.