Question

1. The regulation of aspartate derived amino acids in Arabidopsis thaliana is depicted as an integrated network involving pathway end products that act as allosteric effectors on enzymes in intermediate steps.

   1. Explain the downstream consequence of a reduction in the amount of S-Adenosyl methionine (SAM) on the overall flux of carbon through the various branches of this metabolic pathway.

   2. The first step in converting aspartate into other amino acids is the phosphorylation of aspartate. In A. thaliana, there are five distinct aspartate kinase enzymes, two of which (AK I and AK II) are bi-functional enzymes that also possess homoserine dehydrogenase activity (HSDH I and
      HSDH II, respectively). What is the net effect of combining AK and HSDH activities into one enzyme? How does regulation of AK I/HSDH I and AK II/HSDH II impact the flow of carbon skeletons toward the possible end products in this pathway?

Answer 1