OAA Full Form

What is the full form of OAA?

The full form of OAA is Oxalo acetic acid. Sometimes referred to as oxalo acetic acid, is the full form of OAA. It is an organic molecule that is crystalline and has the chemical formula of;

\mathrm{HO}_2 \mathrm{CC}(\mathrm{O}) \mathrm{CH}_2 \mathrm{CO}_2 \mathrm{H}

In many metabolic processes in mammals, oxalo acetic acid functions as an intermediate in the form of its conjugate base, oxaloacetate. It takes part in processes such as gluconeogenesis, the citric acid cycle, the urea cycle, the glyoxylate cycle, and amino acids and fatty acids synthesis.

Synthesis of OAA

In nature, oxaloacetate can occur in various ways. Malate dehydrogenase catalyzes the oxidation of L-malate in the citric acid cycle and is one of the major pathways. Malate is additionally oxidized by succinate dehydrogenase in a slow process, resulting in the initial product formed as enol-oxaloacetate.

It also results from the hydrolysis of ATP-driven condensation of pyruvate with carbonic acid:

\mathrm{CH}_3 \mathrm{C}(\mathrm{O}) \mathrm{CO}_2{ }^{-}+\mathrm{HCO}_3{ }^{-}+\mathrm{ATP} \rightarrow{ }^{-} \mathrm{O}_2 \mathrm{CCH}_2 \mathrm{C}(\mathrm{O}) \mathrm{CO}_2{ }^{-}+\mathrm{ADP}+\mathrm{Pi}

This activity takes place in the mesophyll of plants and is catalysed by the enzyme phosphoenolpyruvate carboxylase. Aspartic acid can also be trans or deaminated to produce oxaloacetate.

2. Functions of OAA

In the citric acid cycle, oxaloacetate reacts with acetyl-CoA to produce citrate, a reaction that is catalysed by the enzyme citrate synthase. In addition, oxaloacetate also functions in gluconeogenesis, the glyoxylate cycle, fatty acid synthesis, the urea cycle, and amino acid synthesis. Oxaloacetate is a strong inhibitor of complex II.

Gluconeogenesis

A metabolic pathway called "gluconeogenesis" produces glucose from non-carbohydrate substrates through eleven enzyme-catalyzed reactions. The mitochondrial matrix, which is home to pyruvate molecules, serves as the starting point of this process. An enzyme called pyruvate carboxylase is activated by molecules of ATP and water, carboxylates pyruvate molecules. Oxaloacetate is produced by this process. Oxaloacetate is transformed to malate by NADH. To get the molecule out of the mitochondria, this change is required. Malate is again converted to oxaloacetate by oxidation in the cytosol using NAD+. The remaining oxaloacetate is then present in the cytosol, where the rest of the reactions will occur. Oxaloacetate is decarboxylated and phosphorylated by phosphoenolpyruvate carboxykinase to produce 2-phosphoenolpyruvate, which uses GTP as a phosphate source. After further downstream processing, glucose is produced.

Glyoxylate Cycle

A variant of the citric acid cycle is the glyoxylate cycle. It is an anabolic process that is present in bacteria and plants and uses the enzymes malate synthase and isocitrate lyase. Even though some of the cycle's intermediary steps are slightly different from those in the citric acid cycle, oxaloacetate still serves the same function in both processes. This indicates that oxaloacetate also serves as the main reactant and end product in this cycle. Oxaloacetate is a net result of the glyoxylate cycle because its cycle loop contains two molecules of acetyl-CoA.

Fatty Acid Synthesis

Earlier processes involve moving acetyl-CoA from the mitochondria to the cytoplasm, where the enzyme fatty acid synthase is found. Acetyl-CoA is transported as citrate, first produced in the mitochondrial matrix from acetyl-CoA and oxaloacetate. When there is no requirement for energy, this process is transferred to the cytoplasm, where it is broken down into cytoplasmatic acetyl -CoA and oxaloacetate, initiating the citric acid cycle. NADPH is needed in another phase of the cycle to produce fatty acids.

As long as the internal mitochondrial layer is impermeable to oxaloacetate, some of this reducing power is produced when the cytosolic oxaloacetate is returned to the mitochondria. First, NADH is used to convert oxaloacetate to malate. Malate is then decarboxylated to produce pyruvate. This pyruvate can now easily enter the mitochondria, which is more carboxylated to oxaloacetate by pyruvate carboxylase. Thus, a molecule of NADH is created by the transport of acetyl-CoA from the mitochondria into the cytoplasm. The entire spontaneous reaction can be summarised as follows:

\mathrm{HCO}_3^{-}+\mathrm{ATP}+\text { acetyl-CoA } \rightarrow \mathrm{ADP}+\mathrm{P}_{\mathrm{i}}+\text { malonyl-CoA }

Urea Cycle

The urea cycle is a metabolic mechanism that produces urea from one ammonium molecule from degraded amino acids, one bicarbonate molecule, and another ammonium group from aspartate. Hepatocytes frequently use this pathway. NADH is a byproduct of the urea cycle and can be created in two different ways. One of them makes use of oxaloacetate. Fumarate molecules can be found in the cytosol. The fumarase enzyme can convert fumarate into malate. Malate dehydrogenase converts malate into oxaloacetate, which creates a molecule of NADH. Following that, oxaloacetate will be converted back into aspartate since transaminases favour these two keto acids over others. The flow of nitrogen into the cell is maintained by this recycling.

Amino Acid Synthesis

Oxaloacetate and pyruvate create three non-essential and six essential amino acids. By transamination of glutamate, aspartate and alanine are produced from oxaloacetate and pyruvate, respectively.