malaatidehydrogenaasi

Malaatidehydrogenaasi is a hypothetical oxidoreductase enzyme described in theoretical models of central carbon metabolism. The name combines malaate (malate) with dehydrogenase and a characteristic enzymatic suffix, and it is used in computational simulations rather than as a documented natural enzyme. It is not known to occur in any real organism, but it serves as a conceptual tool to explore malate–oxaloacetate interconversion under different cellular conditions.

The enzyme is proposed to catalyze the reversible oxidation of L-malate to oxaloacetate, using NAD+ as the electron acceptor: malate + NAD+ ⇌ oxaloacetate + NADH + H+. As with other malate dehydrogenases, the reaction links glycolytic or gluconeogenic inputs to the mitochondrial tricarboxylic acid (TCA) cycle and related anaplerotic pathways. In model organisms, malaatidehydrogenaasi variants are sometimes described as mitochondrial, with cytosolic forms also considered in alternative flux scenarios.

Structural and genetic notes for this fictional enzyme place malaatidehydrogenaasi as a homodimeric or multimeric protein of modest size, often predicted to have targeting signals for mitochondria or cytosol. No confirmed gene or protein sequence exists in real genomes, and there are no experimentally determined structures. Because it is not empirically observed, its exact kinetic parameters, regulatory features, and substrate specificity remain speculative and are used solely for teaching or modeling purposes.

Significance and limitations: as a constructed example, malaatidehydrogenaasi helps illustrate how alternative malate dehydrogenases could influence redox balance and metabolic flux. It should not be conflated with canonical malate dehydrogenases found in bacteria and eukaryotes.