Characterization of a glutamate-cysteine ligase in Bombyx mori

Abstract Background: Glutamate cysteine ligase (GCL) is a crucial enzyme involved in the synthesis of glutathione (GSH). Despite various studies on glutathione transferase and its essential role in detoxification and resistance to oxidative stress, GSH synthesis has not been described in silkworms to date. Silkworms form part of the lepidopterans that are considered as a model of agricultural pests. This study aimed to understand the GSH synthesis through the GCL in silkworms so that insecticides can be formulated to tackle agricultural pests. Methods and Results: Based on the amino acid sequence and phylogenetic tree, this GCL belonged to group 2 and designated bmGCL. Recombinant bmGCL was overproduced and purified to ensure homogeneity. Biochemical studies revealed that bmGCL uses ATP and Mg2+ to ligate glutamate and cysteine, respectively. High expression levels of bmgcl mRNA and GSH were observed in the silkworm fat body after exposure to insecticides and UV-B. Moreover, we found an increase in bmgcl mRNA and GSH content during pupation in the silkworm fat body. Conclusion: In this study, we found GCL in the silkworm Bombyx mori and its biochemical properties were investigated. These observations indicate that bmGCL might play an important role in the resistance to oxidative stress in B. mori.