Discovery and evaluation of inhibitory activity and mechanism of arylcoumarin derivatives on Theileria annulata enolase by in vitro and molecular docking studies.

In this study, the inhibition potential of 3- and 4-arylcoumarin derivatives on Theileria annulata enolase (TaENO) was assessed for the first time in the literature. Firstly, protein stabilization analyses of TaENO were performed and it was found that the enzyme remains stable with the addition of 6 M ethylene glycol at + 4 °C. Inhibitor screening analyses were carried out using 25 coumarin derivatives on highly purified TaENO (> 95%), and four coumarin derivatives [4-(3,4-dimethoxyphenyl)-6,7-dihydroxy-2H-chromen-2-one (C8); 4-(3,4-dihydroxyphenyl)-7,8 dihydroxy-2H-chromen-2-one (C9); 4-(3,4-dihydroxyphenyl)-6,7-dihydroxy-2H-chromen-2 one (C21); and 3-(3,4-dihydroxyphenyl)-7,8-dihydroxy-2H-chromen-2-one (C23)] showed the highest inhibitory effects with the IC50 values of 10.450, 13.170, 8.871 and 10.863 µM, respectively. The kinetic results indicated that these compounds inhibited the enzyme by uncompetitive inhibition. In addition, the successful binding of the most potent inhibitor (C21) into TaENO was confirmed by using MALDI-TOF mass spectrophotometry. Molecular docking analyses have predicted that C8 and C21 coumarin derivatives which showed high inhibitory effects on TaENO were interacted with high affinity to the potential regions out of the active site. Taken together, these coumarin derivatives (C8, C9, C21 and C23) are first known potent, nonsubstrate, uncompetitive inhibitors of TaENO and these results will facilitate further in vitro and in vivo analysis toward structure-based drug design studies.

Functional analyses of dipeptide and pentapeptide insertions on Theileria annulata enolase by site-directed mutagenesis and in silico approaches.

Theileria annulata enolase (TaENO) could be assessed as a druggable target for tropical theileriosis treatment. The parasite enzyme plays an important role in many cellular functions and carries some structural differences like dipeptide (262EK263) and pentapeptide (103EWGYC107) insertions from the host enzyme, Bos taurus enolase. In this study, the functional effects of these insertions on TaENO activity were analyzed by in vitro site-directed mutagenesis and in silico molecular docking analyses for the first time in the literature. In vitro results showed that, although the deletion of the pentapeptide insertion (TaENOΔEWGYC) reduced the enzyme activity slightly, the removal of the dipeptide insertion (TaENOΔEK) halted it. Also, molecular docking results revealed that the deletion of these insertions affected the substrate binding affinity of the mutant enzymes. The active site of TaENOΔEK exhibited a small decrease of substrate binding affinity compared to the active site of TaENOΔEWGYC relative to the wild type TaENO. Although we conclude that both regions could be evaluated as possible drug-binding sites to inhibit TaENO in further studies, these results indicate that the dipeptide insertion could be a more promising drug binding site than the pentapeptide insertion.

A study of Bos taurus muscle specific enolase; biochemical characterization, homology modelling and investigation of molecular interaction using molecular docking and dynamics simulations.

Tropical theileriosis caused by Theileria annulata obligate parasite that infect ruminant animals, including Bos taurus. The disease results massive economic losses in livestock production worldwide. Here we describe cloning, expression and both biochemical and structural characterization of beta enolase from Bos taurus in vitro and in silico. The interconversion of 2­phosphoglycerate to phosphoenolpyruvate was catalyzed by enolase is a metalloenzyme in glycolytic pathway and gluconeogenesis. Enolase from Bos taurus was cloned, expressed and the protein was purified at 95% purity using cobalt column by affinity chromatography. The optimum enzymatic activity was calculated at pH 6.5. For the first time in the literature, the kinetic parameters of the enzyme, Vmax and Km, were measured as 0.1141 mM/min and 0.514 mM, respectively. Besides, Bos taurus enolase 3-dimensional structure was built by homology modelling to be used in silico analyses. The interactions of the enzyme-substrate complex were elucidated by molecular dynamics simulations for 100 ns. These interactions were found to be the same as experimentally determined interactions in yeast. These results would enable further structure based drug design studies with the biochemical characterization of the host organism Bos taurus enolase enzyme in vitro and the elucidation of behavior of enzyme-substrate complex in silico.

Comprehensive structural analysis of the open and closed conformations of Theileria annulata enolase by molecular modelling and docking.

Theileria annulata is an apicomplexan parasite which is responsible for tropical theileriosis in cattle. Due to resistance of T. annulata against commonly used antitheilerial drug, new drug candidates should be identified urgently. Enolase might be a druggable protein candidate which has an important role in glycolysis, and could also be related to several cellular functions as a moonlight protein. In this study; we have described three-dimensional models of open and closed conformations of T. annulata enolase by homology modeling method for the first time with the comprehensive domain, active site and docking analyses. Our results show that the enolase has similar folding patterns within enolase superfamily with conserved catalytic loops and active site residues. We have described specific insertions, possible plasminogen binding sites, electrostatic potential surfaces and positively charged pockets as druggable regions in T. annulata enolase.

Biochemical and in silico Characterization of Recombinant L-Lactate Dehydrogenase of Theileria annulata.

Theileria annulata is a parasite that causes theileriosis in cattle. Reports about drug resistance made essential to develop new drug. LDH of Theileria schizonts is the vital enzyme for its anaerobic metabolism. TaLDH gene was first cloned into pGEM-T cloning vector with two introns in our previous study. Here we report cloning of TaLDH without introns into pLATE 31 vector in E. coli BL21(DE3). Protein was in an inactive form. Two mutations were fixed to express the active protein. Protein was purified by affinity chromatography and evaluated by SDS-PAGE and size exclusion chromatography. Optimum pH of enzyme was performed in pH 7.5, and enzyme was stabilized at 20-40 °C. Enzyme kinetics of recombinant TaLDH were found to be in the direction of pyruvate to lactate K m 0.1324 and K i 4.295 mM, k cat, 44.55/s and k cat /K m, 3.3693 × 10(5)/M/s. 3D structure of TaLDH was predicted, and possible drug binding sites were determined by homology modelling.