Enolase as a plasminogen receptor
Enolase, as a plasminogen receptor and activator localized on the surface of several helminths, can interact with the host fibrinolytic system (Yang et al., 2010, Du et al., 2009, de la Torre-Escudero et al., 2010). The enzyme is also one of excretory/secretory (ES) products in some helminths, such as F. hepatica (Bernal et al., 2004) and C. sinensis (Wang et al., 2011). On the contrary, no enolase is found in ES products of Trichinella spiralis (Nakada et al., 2005). In the present study, TmENO was detected in the T. multiceps adult, the metacestode worm by RT-PCR and western-blotting, which suggested enolase is indeed a key protein in the tyramide metabolism and development of T. multiceps. In addition, we speculated that enolase was found in cyst fluid of T. multiceps may be related to the parasite clearance or an unknown transport mechanism for protein secretion by the worm.
As enolase is a multifunctional metabolic enzyme, the enzymatic activity of the rTmENO protein was analyzed in the present study. The results showed that the enzymatic reaction speed of the forward conversion from 2-PGA to PEP was faster than that of the reverse conversion from PEP to 2-PGA at pH7.5 and occurred in 20–30min (Fig. 4), we presumed that the reciprocal conversion depended on the optimal pH and concentration of Mg. The speed of the conversion may also be dependent on the doses of the substrate (2-PGA or PEP) and enolase; however, to the best of our knowledge, the speed of the reverse conversion (from PEP to 2-PGA) is not known for other organisms. Recent studies have demonstrated that the optimal pH for recombinant enolase is pH7.0–8.0 in enzymatic reactions (Yang et al., 2010, Han et al., 2012).
Conclusions In the current study, we cloned the TmENO gene from T. multiceps, and RT-PCR showed that it was expressed in adult and the metacestode of the life cycle, and then analyzed its enzymatic activity and plasminogen-binding activity.
Acknowledgements This study was supported by the Science Fund for Creative Research Groups of Gansu Province (Grant No.1210RJIA006) and the National Key Project of Scientific and Technical Supporting Program (No.2007BAD40B04) and was partially supported by the National Beef Cattle and Yak Industrial Technology System, NBCITS, MOA (No.CARS-38).
Introduction Avian coccidiosis, an important parasitic disease caused by Eimeria spp., an apicomplexan protozoan parasite, is responsible for a substantial economic burden globally in the avian industry (Györke et al., 2013, Williams, 1999). As the most virulent Eimeria spp. species, has a complex lifestyle, including exogenous (sporogony) and endogenous developmental stages (schizogamy and gametogony, respectively). Although coccidian vaccines have been extensively studied as a novel strategy to provide protection against coccidiosis (Yin et al., 2014, Mansoori and Modirsanei, 2012, Song et al., 2013), these vaccines are not widely used in the poultry industry because of their poor stability. Thus, the control of coccidiosis still mainly depends on anti-coccidiosis drugs. Unfortunately, the large-scale and long-time use of anticoccidials has led to the emergence of anticoccidial resistance problems (Stephan et al., 1997, Kawazoe and Fabio, 1994, Arabkhazaeli et al., 2013). Therefore, studies have been conducted recently to search for novel therapeutic drugs and strategies against coccidiosis. Recently, a novel anti-coccidiosis triazine compound, acetamizuril, was synthesized by the Shanghai Veterinary Research Institute of the Chinese Academy of Agricultural Sciences; its structure is similar to those of diclazuril and toltrazuril. Previous studies have shown that this novel compound has a high anticoccidial activity with an anticoccidial index above 180 and an acceptable safety profile (unpublished data). Enolase, a key glycolytic enzyme, is an essential cytoplasmic enzyme that catalyzes the dehydration of 2-phosphoglycerate to phosphoenolpyruvate in the final steps of the glycolytic pathway (Yang et al., 2014). Enolases have highly conserved amino acid sequences and possess a wide range of additional functions beyond their classical role in glycolysis (Raghunathan et al., 2014, Karina et al., 2012). In E. tenella, enolase also plays a vital role in the interaction of the parasites with host cells (Labbé et al., 2006).