Studies on enzymatic properties and stress resistance of glutathione peroxidase (GPX) from Larix kaempferi

  Objective  Glutathione peroxidase (GPX) is one of the key enzymes in the plant’s enzymatic active oxygen scavenging mechanism. Conducting enzymatic characteristics and stress resistance research on Larix kaempferi GPX can supply and improve genetic resources and provide theoretical basis for exploring the molecular mechanism of glutathione peroxidase stress resistance.

  Method  The glutathione peroxidase genes were cloned using the stem tissue of Larix kaempferi as a template. In this study, bioinformatics analysis and subcellular localization research were conducted. The GPXs were induced and purified for in vitro enzymatic assays, and verified to have the stress resistance through spotting experiment and growth curve experiment.

  Result  Two GPX genes were cloned from the stem of Larix kaempferi, named LkGPX2 and LkGPX3, both of which contained complete characteristic conserved motifs. LkGPXs were grouped together with the PmGPX and PeGPX in a phylogenetic tree, which were stress-resistant. Subcellular localization showed that both LkGPX2 and LkGPX3 proteins were localized in the nucleus and cytoplasm. Using thioredoxin (Trx) as an electron donor for in vitro enzymatic activity, LkGPX2 and LkGPX3 had catalytic activity on H₂O₂, t-BHP and Cum-OOH. The catalytic activities of LkGPX2 were (0.402 ± 0.037) U/mg, (0.424 ± 0.018) U/mg, (0.425 ± 0.009) U/mg, and the catalytic activities of LkGPX3 for the three substrates were (0.397 ± 0.027) U/mg, (0.449 ± 0.028) U/mg, and (0.407 ± 0.021) U/mg, respectively. Moreover, the results of stress treatment experiment indicated that LkGPX2 and LkGPX3 could improve the tolerance of Escherichia coli to simulated drought stress and salt stress.

  Conclusion  Larix kaempferi glutathione peroxidase (GPX) is capable of scavenging active oxygen as well as responding to abiotic stresses.