Malonate

[adaffara]

Hi. I am suppose to determine malonate's site of action in the citric acid cycle. The results tell that malonate is first acted upon by succinate, then fumarate, malate, and lastly pyruvate where it can be converted to acetyl-CoA which feeds the acetyl group into the citric acid cycle. The enzyme that inhibits malonate is succinate dehydrogenase. Onece I have malonate's site of action explain what would happen to the concentration of each of the following molecules: citrate, isocitrate, a-ketoglutarate, succinate, oxaloacetate, malonate, ADP, and ATP in the experiment if you treated these mitochondria with excess amounts of malonate? I'm not sure where to begin. Any suggestions would be helpful. Thank you.

[JackBean]

1) malone is not inhibited by enzyme, but vice versa!

2) I guess the question is, what will happen, if you block TCA cycle?

[adaffara]

So malonate is a competative inhibitor acted upon by succinate dehydrogenase (which is the enzyme)? If excess malonate were to act upon the citric acid cycle then the cycle would cease because it is an competative inhibitor and would eventually win over the substrate. Because the TCA cycle feeds further synthesis, stopping one site would stop all the others?

[JackBean]

yes, probably

However, some chemicals will be accumulated due to the inhibition, but others probably decreased, because they will be used before the cycle stops, however, not replenished