Molecular Characteristics of the Malate Dehydrogenase (MDH) Gene Family in (Cestoda: Diphyllobothriidea).

The plerocercoid larva of can cause a parasitic zoonosis-sparganosis. Malate dehydrogenase (MDH) plays a very important role in the life activities of parasites. However, little is known about the MDH family in . We identified eight new MDH members in in this study. Clustering analysis divided MDHs into two groups and revealed patterns similar to the conserved motif organization. RT-qPCR suggested that five MDHs were highly expressed in the mature proglottid and that three MDHs were highly expressed in the gravid proglottid. Phylogenetic analysis revealed that MDHs contain both conserved family members and members in the process of further diversification. rMDH has an NAD binding domain, a dimer interface and a substrate binding domain. Natural MDH was immunolocalized in the tissues and follicles around the uterus in the mature or gravid proglottid and eggshells. The maximum forward and reverse reaction activities of rMDH were observed at pH 8.5 and 9.0, respectively. The optimum temperature for enzyme activity was 37 °C in the forward reaction and 40 °C in the reverse reaction. These results lay the foundation for studying the molecular functions and mechanisms of MDHs in and related taxa.