Question

a mutant mammalian liver cell line requires a non-essential amino acid, aspartate, for growth. In this cell line, it was found that the glycolytic pathway and TCA cycle are normal, also the aspartate transaminase and PDH complex function normally. If cells from this line are transferred from a medium containing aspartate to one without aspartate, cell growth is arrested and intracellular acetyl-sCoA concentrations increase. The mutant cell line is defective in

a. Citrate synthase

b. Pyruvate Kinase

c. Pyruvate dehydrogenase

d. Malate dehydrogenase

e. pyruvate carboxylase and magic enzyme

Answer 1

The correct answer is a) Citrate synthase because when the cells get arrested the acetyl coA concentration increases, hence the enzyme citrate synthase is defective as this enzyme converts all acetyl coA into citrate which is a non essential amino acid similar to aspartate which is now absent from medium.

Hope this helps.