Evaluating the effects of metal ions on malate dehydrogenase enzyme activity in Watermelon.

Abstract

Malate Dehydrogenase (MDH) is an essential enzyme in the cellular respiration pathway known as the Tricarboxylic Acid Cycle. Using NAD⁺ or NADP⁺ as a cofactor, MDH catalyzes the reversible conversion of oxaloacetate to malate. It can be found in plants, bacteria, and animals. However, some metal ions, such as Cu²⁺, Zn²⁺, and Pb²⁺, can decrease MDH activity. In this study, the recombinant MDH protein (His-MDH) of watermelon was purified and quality tested by SDS-PAGE. The average protein concentrations of elution, cell lysate, and wash were 0.37 mg/mL, 2.23 mg/mL, and 0.24 mg/mL, respectively. According to SDS-PAGE, the size of the purified protein was approximately 37 kD, suggesting the purification of the correct protein.

   The enzyme activity of the MDH protein will be tested in the presence of metal ions such as MgSO₄, NiSO₄, ZnSO₄, CuSO₄, and PdCl₂, which have been shown to inhibit dehydrogenase enzymes. Our results provide valuable insight on how different metal ions present in the environment can affect the cell respiration of organisms by affecting the malate dehydrogenase enzyme. Further studies on the roles of metal ions in the TCA cycle and related metabolism, as well as the mechanisms by which metal ions inhibit enzyme activity, will be beneficial in understanding ways to improve soil conditions for higher crop production and for the understanding of evolutionary processes.