Question

cOO COO CH2 CH2 COO coo cOO Citrate Isocitrate

1a) What is the oxidation state of the carbon bonded to the hydroxyl group on Citrate and Isocitrate?

1b) What property of isocitrate makes it a better substrate for oxidation?

Answer 1

1 a ) the original positions of the hydrogen atom and hydroxyl group in citrate are reversed. Thus, the overall result of the reaction is to isomerise citrate to isocitrate and, in so doing, to rearrange the oxidation states of C 2 and C3; the former is oxidised (-2-->0) while the latter is reduced by the same amount (+1-->-1).

2 b ) the  isocitrate, produced from the isomerization of citrate, undergoes both oxidation and decarboxylation. Using the enzyme Isocitrate Dehydrogenase (IDH), isocitrate is held within its active site by surrounding arginine, tyrosine, asparagine, serine, threonine, and aspartic acid amino acids.

by using NAD+/NADP+ as an electron accepting cofactor isocitrate easily undergoing in oxidation process.