In: Biology
What role does oxalloacetate play in the TCA cycle? What is the role of oxalloacetate gluconeogenesis?
Oxaloacetate is a four carbon
molecule which initiates the first step of citric acid cycle and is
regenerated at the end of cycle. Oxaloacetate reacts with acetylCoA
to form citrate by citrate synthase and the cycle continues further
. Its role is shown in the image attached.
Gluconeogenesis is a pathway which
generates glucose from non carbohydrate sources.The initial steps
takes place in the mitochondrial matrix, where pyruvate molecules
are found. A pyruvate molecule is carboxylated by a pyruvate
carboxylase enzyme, activated by a molecule each of ATP and water
thereby forming oxaloacetate. NADH reduces oxaloacetate to malate
to transport the molecule out of the mitochondria. Once in the
cytosol, malate is oxidized to oxaloacetate in cytosol where the
rest of reactions take place. Oxaloacetate is further
decarboxylated and phosphorylated by phosphoenolpyruvate
carboxykinase and becomes 2-phosphoenolpyruvate using guanosine
triphosphate (GTP) as phosphate source. Glucose is produced at the
end. The steps of gluconeogensis is shown in image
attached.