oksaloasetaati

Oksaloasetaatti is a dicarboxylic acid that plays a crucial role in intermediary metabolism. It is a four-carbon molecule with the chemical formula C4H4O5. Oksaloasetaatti is a key intermediate in the citric acid cycle, also known as the Krebs cycle or the TCA cycle. In this cycle, it is formed by the condensation of acetyl-CoA with oxaloacetate, catalyzed by citrate synthase, and is subsequently regenerated. Beyond its central role in energy production, oksaloasetaatti is also involved in gluconeogenesis, the synthesis of glucose from non-carbohydrate precursors. It is a substrate for the enzyme phosphoenolpyruvate carboxykinase (PEPCK), which catalyzes the conversion of oxaloacetate to phosphoenolpyruvate, a rate-limiting step in gluconeogenesis. Furthermore, oksaloasetaatti is a component of the malate-aspartate shuttle, a mechanism for transporting reducing equivalents across the mitochondrial membrane. Its synthesis can occur through the carboxylation of pyruvate, catalyzed by pyruvate carboxylase, an enzyme particularly active in the liver and kidneys. This reaction requires ATP and bicarbonate. Oksaloasetaatti is also generated from aspartate via the enzyme aspartate aminotransferase. The concentration and flux of oksaloasetaatti are tightly regulated to maintain cellular energy balance and metabolic homeostasis.