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In this study, dienelactone hydrolases (TfdEI and TfdEII) located on plasmid pJP4 of  Cupriavidus necator  JMP134 were cloned, purified, characterized and three dimensional structures were predicted.  tfdEI  and  tfdEII  genes were cloned into pET21b vector and expressed in  E. coli  BL21(DE3). The enzymes were purified by applying ultra-membrane filtration, anion-exchange QFF and gel-filtration columns. The enzyme activity was determined by using  cis -dienelactone. The three-dimensional structure of enzymes was predicted using SWISS-MODEL workspace and the biophysical properties were determined on ExPASy server. Both TfdEI and TfdEII (M r  25 kDa) exhibited optimum activity at 37°C and pH 7.0. The enzymes retained approximately 50% of their activity after 1 h of incubation at 50°C and showed high stability against denaturing agents. The TfdEI and TfdEII hydrolysed  cis -dienelactone at a rate of 0.258 and 0.182 µMs −1 , with a K m  value of 87 µM and 305 µM, respectively. Also, TfdEI and TfdEII hydrolysed  trans -dienelactone at a rate of 0.053 µMs −1  and 0.0766 µMs −1 , with a K m  value of 84 µM and 178 µM, respectively. The TfdEI and TfdEII k cat /K m  ratios were 0.12 µM −1 s −1 and 0.13 µM −1 s −1  and 0.216 µM −1 s −1  and 0.094 µM −1 s −1  for for  cis - and  trans -dienelactone, respectively. The k cat /K m  ratios for  cis -dienelactone show that both enzymes catalyse the reaction with same efficiency even though K m  value differs significantly. This is the first report to characterize and compare reaction kinetics of purified TfdEI and TfdEII from  Cupriavidus necator  JMP134 and may be helpful for further exploration of their catalytic mechanisms.

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Two Structurally Different Dienelactone Hydrolases (TfdEI and TfdEII) from Cupriavidus necator JMP134 Plasmid pJP4 Catalyse Cis- and Trans-Dienelactones with Similar Efficiency