oksalaattisia

Oxaloacetates are four-carbon dicarboxylates that exist in cells primarily as the oxaloacetate dianion under physiological conditions. The term encompasses oxaloacetic acid and related salts. Oxaloacetate is a central metabolic intermediate involved in multiple pathways and can interconvert with several other metabolites depending on cellular needs.

In metabolism, oxaloacetate plays a key role in the tricarboxylic acid (TCA) cycle. It condenses with acetyl-CoA to form citrate via citrate synthase, initiating the cycle. Oxaloacetate is continually regenerated as the cycle proceeds, providing carbon skeletons for energy production and biosynthesis. It also serves as an anaplerotic substrate, replenishing TCA intermediates when they are siphoned off for other pathways.

Oxaloacetate participates in gluconeogenesis, where it is formed from pyruvate by pyruvate carboxylase in mitochondria and then converted to phosphoenolpyruvate by PEP carboxykinase (in mammals) or transported to the cytosol for further processing. It can also be transaminated to aspartate by aspartate aminotransferase, linking nitrogen and carbon metabolism (oxaloacetate plus glutamate yields aspartate and α-ketoglutarate). In many organisms, oxaloacetate is involved in the malate–aspartate shuttle, which transfers reducing equivalents between mitochondria and cytosol.

In plants, bacteria, and animals, oxaloacetate is also a precursor for other biosynthetic routes, including amino acid production and, in C4 photosynthesis, initial carbon fixation via phosphoenolpyruvate carboxylase to oxaloacetate. Overall, oxaloacetate acts as a metabolic hub, connecting energy metabolism with anabolic processes and nitrogen metabolism.