Oxaloacetic acid
- Oxobutandisäure
- Oxobernsteinsäure
White to light yellow crystalline solid
Fixed
161 ° C ( decomposition)
Readily soluble in water
Risk
Template: Infobox chemical / molecular formula search available
Oxaloacetic acid is a metabolite of the citric acid cycle Oxodicarbonsäure and as a major hub in metabolism. Its salts are called Oxalacetate (OA ).
Occurrence
Oxaloacetic acid comes in higher plants at high concentrations.
Properties
Oxaloacetic acid as the dicarboxylic acid is both α - and β -keto acid and shows the reactions of the two classes of substances:
- As α -keto acid it undergoes nucleophilic attack wherein it can be transferred by transamination of the C- α in the homologous amino acid aspartic acid;
- In the initial reaction of the citric acid cycle acetyl -CoA is through their H -acidic methylene group, the nucleophile, where citrate is produced;
- As β -keto acid, it shows the instability of this substance class and passes through decarboxylation catalyzed by the malic enzyme in a (ME) partial reaction to pyruvate ( Pyr) or
- In a by phosphoenolpyruvate carboxykinase ( PEPCK ) catalyzed reaction in phosphoenolpyruvate ( PEP) over; the latter is an important partial reaction of gluconeogenesis;
- ATP effort enables conversely, the carboxylation of pyruvate to oxaloacetate by the biotin - dependent enzyme pyruvate carboxylase. This process is the most important anaplerotic (ie filling up the citric acid cycle ) reaction;
- Oxaloacetate can accommodate two reducing equivalents per mole and transport (after transition into malate, time ) on the mitochondria ( inside ) membrane. Both directions of transport are possible: the reaction sequence OA → time | | time → OA leads to reducing equivalents from the cytosol of the respiratory chain and serves the ATP - profit;
- The rear passing through the same reaction sequence transported (eg Citratüberschuss ) reducing equivalents to the cytosol. These may be used there in the form of NADPH, H for the synthesis of fats. At the same time for this operation is the substrate acetyl- CoA ( from citrate ) is available.