Tissue distribution and properties of glutathione S-transferases in Apis cerana cerana Fabricius and Apis mellifera ligustica Spinola
Qingyun Diao, Kai Yuan, Pei Liang, Xiwu Gao
The glutathione S-transferases (GSTs) have been recognized to play an important role in the detoxification of xenobiotics. The tissue distribution and activities of GSTs in Apis cerana cerana Fabricius and Apis mellifera ligustica Spinola were assayed using 1-chloro-2,4- dinitrobenzene (CDNB) as substrate. GSTs were present at all the developmental stages of honeybee and widely distributed in different organs. GSTs from the midgut of both species showed the highest activity among all the detected organs. The enzymes were preferentially present in cytosol fraction of midgut. GSTs activities of each organ in A. cerana were lower than those in A. mellifera. In A. cerana, the activity and Michaelis Menten (Km) value of GSTs increased along with the development, no significant difference of activity and Km was observed among different tissues. The enzymes activities increased rapidly and reached a maximum at the pupal stage to 0.081μmol.min-1.mg-1 protein. A. mellifera samples represented a different pattern. Significant differences of activity and Km value were observed in different tissues. The GSTs in the midgut had the highest Km value.However, the highest activity was found in the larvae and the lowest in the adult. The GSTs activities in drone were higher than those in worker bee. During the life span of A. mellifera worker bee, enzymes activities fluctuated between 0.2 and 0.4 μmol.min-1.mg-1pro. from the first day to 20th day and reached a peak on day 21 of adulthood. Significant differences of specific activity and kinetic parameters of GSTs were observed among five honeybee subspecies. The highest activity was in A. mellifera caucasica and the lowest in A. cerana cerana. The GSTs from A. mellifera anatolica had the highest Km and those from caucasica had the lowest. In A. mellifera, it was GSTs from anatolica that had the highest Vmax and those from caucasica had the lowest. The GSTs from A. cerana had a higher affinity for CDNB than those from A. mellifera.