malatadehydrogenaasin

Malatatehydrogenaasin, also known as malate dehydrogenase (MDH), is an enzyme that catalyzes the reversible oxidation of L-malate to oxaloacetate. This reaction is a crucial step in both the citric acid cycle (also known as the Krebs cycle or TCA cycle) and the malate-aspartate shuttle. In the citric acid cycle, MDH is responsible for the final step, regenerating oxaloacetate, which is then available to condense with acetyl-CoA to begin another cycle. This process occurs in the mitochondria of eukaryotic cells.

There are different forms of malate dehydrogenase found in various cellular compartments. Mitochondrial malate dehydrogenase is essential for cellular respiration. Cytosolic malate dehydrogenase plays a role in gluconeogenesis and the malate-aspartate shuttle. The malate-aspartate shuttle is particularly important in the liver and heart for transferring reducing equivalents from cytosolic NADH into the mitochondria, thereby enabling oxidative phosphorylation.

The enzyme utilizes NAD+ as a cofactor, which is reduced to NADH during the oxidation of malate. The reaction is highly reversible, meaning it can proceed in either direction depending on the cellular conditions and substrate concentrations. Malate dehydrogenase is a highly conserved enzyme across many species, highlighting its fundamental importance in metabolism. Its activity is regulated by factors such as substrate availability and the ratio of NAD+ to NADH. Dysfunction of malate dehydrogenase can have significant metabolic consequences.