94118-83-9 Enzyme Preparation MDH Malate Dehydrogenase metal ions

Malate dehydrogenase (MDH) temperature and the influence of metal ions；MDH；Enzyme；94118-83-9

Malate dehydrogenase (MDH) temperature and the influence of metal ions
Malate dehydrogenase (MDH) is commonly found in various organisms such as animals, plants, bacteria, etc. It is one of the key enzymes in biological sugar metabolism and can catalyze the reversible conversion between malate and oxaloacetate. MDHs play an important role in a variety of physiological activities of cells, including mitochondrial energy metabolism and plant active oxygen metabolism.

Biochemical properties of malate dehydrogenase
1. Optimal pH and Optimal Temperature
The optimal pH value of MDHs is relatively alkaline, about 8.0. For example, MDH of Streptomyces and E. coli (EcMDH) has the highest enzyme activity at pH 8.1. The optimal reaction temperature of MDHs is 40～65℃. For example, the optimum temperature of Bacillus subtilis MDH and porcine myocardial MDH is about 50℃, and Bacillus stearothermophilus (BMDH) has good stability at 65℃. When the temperature tends to extremes, the MDHs of most species are not very active, but MDH from psychrophilic bacteria (AaMDH) still maintains high activity at about 4℃, and MDH of thermophilic bacteria can still maintain at 90℃ The activity of about 1h, this difference may be caused by the preference of certain residues in the active site, the distribution of substrate and cofactor charges, and the ion-pair interaction between subunits.

2. Thermal stability
EcMDH and Bacillus subtilis MDH have poor thermal stability. Bacillus stearothermophilus BsMDH is quite stable at high temperatures. The thermophilic bacteria AaMDH is heat-labile, which is presumably related to the number of hydrogen bonds, the number and position of proline or glycinase molecules, and their interaction. In low temperature environment, glycerol is the best stabilizer to maintain MDHs activity, while cyclopolyol and sorbitol can maintain MDHs activity at high temperature. The principle of this stabilization may be that the interaction between the hydroxyl group and the enzyme molecule or the alcohol reduces the dielectric constant of the medium and strengthens the hydrophobic effect of the enzyme molecule, so that the enzyme egg is less affected by water molecules.
3. The influence of metal ions
Various charged ions have different effects on the activity of MDHs and the stability of proteins. The study of different metal ions on mung bean MDH shows that: K+ has an activating effect; Mg2+ and Ca2+ have little effect on enzyme activity; Zn2+, P2+ and Cu2+ do Enzyme activity has different degrees of inhibition, of which Cu2+ inhibition is the strongest. When its concentration is 1M, 97% of enzyme activity is inhibited.
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