Molecular and biochemical characterisation and recognition by the immune host of the enolase of the abomasal nematode parasite Teladorsagia circumcincta.

A 1299 bp full length cDNA encoding Teladorsagia circumcincta enolase ( Teci ENO) was cloned, expressed in Escherichia coli and the recombinant protein purified and its kinetic properties determined. Helminth enolase sequences were used to construct a phylogenetic tree. The predicted protein consisted of 433 amino acids and was present as a single band of about 50 kDa on SDS-PAGE. Multiple alignments of the protein sequence of Teci ENO with homologues from other helminths showed 98% similarity with Haemonchus contortus enolase, 78–95% similarity to other nematode sequences and 72–75% similarity to cestode and trematode enolases. Substrate binding sites and conserved regions were identified and were completely conserved in other homologues. The optimum pH for Teci ENO activity at 25 °C was pH 7, the K m for 2-phophoglycerate 0.09 ± 0.04 mM and the V max was 604 ± 6 nmol min −1 mg −1 protein (both mean ± SD, n = 2). Teci ENO activity was inhibited by 11.5% by 1 mM citrate (p < 0.001). Antibodies in both serum and saliva from field-immune, but not nematode-naïve, sheep recognised recombinant Teci ENO in enzyme-linked immunosorbent assays. The recognition of the recombinant protein by antibodies generated by exposure of sheep to native enolase indicates similar antigenicity of the two proteins. [ABSTRACT FROM AUTHOR]