Cloning, expression and characterisation of short-chain dehydrogenase/reductase SDR12 (A0A7I5E7J1) from a parasitic nematode Haemonchus contortus

Short-chain dehydrogenases/reductases (SDRs) play a crucial role in xenobiotic and eobiotic metabolism in all organisms. In the parasitic nematode Haemonchus contortus , SDRs represent potential contributors to drug resistance and potential drug targets. Among them, Hco_sdr12 (WormBaseAcc: HCON_0049110) seemed to be the most interesting as its constitutive expression was higher in all developmental stages of H. contortus from the drug-resistant strain in comparison to the drug-susceptible strain. Moreover, Hco_sdr12 was inducible by exposure of H. contortus adult males with the anthelmintic drug flubendazole. With an aim to know more about this enzyme, Hco_ SDR12 (UniprotAcc: A0A7I5E7J1) was cloned, purified and characterised. The corresponding gene was cloned into the pET22b(+) vector system, the protein was overexpressed in E. coli and purified by Ni-affinity chromatography. The various xenobiotic and eobiotic compounds, including flubendazole, were tested as potential substrates of Hco_ SDR12. Although this enzyme did not reduce flubendazole, significant reductase activities toward many other substrates were found with a preference for NADPH as a coenzyme. Glyceraldehyde, metyrapone and ketoprofen were used for kinetic studies. According to bioinformatic analysis, Hco_ SDR12 shares the highest similarity with hydroxysteroid dehydrogenase-like protein 2, which indicates its involvement in lipid metabolism. Even though Hco_ SDR12 cannot deactivate flubendazole, it can deactivate other xenobiotics with a carbonyl group. Its higher expression might help nematodes to protect themselves against reactive compounds and to gain energy from lipides more effectively.