Bacopa monniera recombinant mevalonate diphosphate decarboxylase: Biochemical characterization

Abstract Mevalonate diphosphate decarboxylase (MDD; EC 4.1.1.33) is an important enzyme in the mevalonic acid pathway catalyzing the Mg 2+ -ATP dependant decarboxylation of mevalonate 5-diphosphate (MVAPP) to isopentenyl diphosphate (IPP). Bacopa monniera recombinant MDD (BmMDD) protein was overexpressed in Escherichia coli BL21 (DE3) strain and purified to apparent homogeneity. K m and V max for MVAPP were 144 μM and 52 U mg −1 respectively. The values of turnover ( k cat ) and k cat /K m for mevalonate 5-diphosphate were determined to be 40 s −1 and 2.77 × 10 5  M −1  s −1 and k cat and k cat /K m values for ATP were found to be 30 s −1 and 2.20 × 10 4  M −1  s −1 , respectively. pH activity profile indicated the involvement of carboxylate ion, lysine and arginine for the activity of enzyme. The apparent activation energy for the BmMDD catalyzed reaction was 12.7 kJ mol −1 . Optimum pH and temperature for the forward reaction was found to be 8.0 and 45 °C. The enzyme was most stable at pH 7 at 20 °C with the deactivation rate constant ( K d * ) of 1.69 × 10 −4 and half life ( t 1/2 ) of 68 h. The cation studies suggested that BmMDD is a cation dependant enzyme and optimum activity was achieved in the presence of Mg 2+ .