Identification of an enolase gene and its physiological role in Spirometra mansoni

Enolase is a crucial enzyme involved in the glycolytic pathway and gluconeogenesis in parasites. It also has been reported to function as a plasminogen receptor and may be involved in tissue invasion. In this study, the biochemical properties of the enolase of Spirometra mansoni ( Sm enolase) were investigated. The Sm enolase gene was found to cluster closely with the enolase genes of Clonorchis sinensis and Echinococcus granulosus , and some functional motifs were identified as conserved. Sm enolase was confirmed to be a component of the secretory/excretory products (ESPs) and a circulating antigen of spargana. Recombinant Sm enolase expressed in vitro was able to bind to human plasminogen. Sm enolase was detected in the eggs, testicles, and vitellaria of adult worms and the tegument of spargana. The transcription level of Sm enolase was highest at the gravid proglottid stage. When spargana were cultured with glucose of different concentration in vitro, it was observed that the expression levels of Sm enolase in the low-glucose groups were consistent with that of Sm enolase in vivo. These results indicate that Sm enolase is a critical enzyme involved in supplying energy to support the development and reproduction of the parasite, and it may also play a role in sparganum invasion.