Why is the conc of Oxaloacetate low in the cell although it is acceptor of acetyl groups in the TCA cycle?

Question

Also - which properties of the enzymes of the TCA cycle ensure that the concentration of oxaloacetate cannot rise too high?

Answer 1

Ha Ha I just had an exam on the TCA.



oxaloacetate is also used to make the Aspartate and Asparagine which are used to make Pyrimidines. Oxaloacetate is also used with the enzyme PEP carboxylase to yield PEP (Phosphoenolpyruvate). So if a cell is trying to make biosynthetic products (amino acids, nucleotides, heme, ect.) it may stop the TCA cycle and use its intermediates here instead.



Another explanation



Malate is oxidized (losses electrons) to form oxaloacetate (step 8 of TCA). The electrons lost are added onto NAD+ to form NADH. If there is a high concentration of NADH, there is normally a low concentration of NAD+ meaning that the malate stays as malate because it cannot lose its electrons to NAD+ to yield oxaloacetate.