Question

PDH and TCA Pathway Assignment Start with one molecule of pyruvate and write all of the reactions through one round of TCA, including all other substrates, cosubstrates as needed.

• Include structures and full names of all of the substrates (you do not have to include structures of the cosubstrates and cofactors)

• Include names of each enzyme catalyzing each reaction. • Identify the decarboxylation reactions with X, the redox reactions with *’s and the substrate level phosphorylations with O’s.

• Include the allosteric effectors at all points where applicable. You do not need to include structures and you may use abbreviations for the nucleotide based effectors.

• Go back to your reactions. Label the carbonyl carbon of pyruvate as C14.

Follow this carbon through the reactions (labeling as C14) until the carbon is released as 14CO2.

Be able to predict where radiolabeled CO2 will be released if you started with oxaloacetate labeled at C4.

Be able to predict where the radiolabeled C will end up if you started with pyruvate being labeled at C3.

Be able to predict where the radiolabeled C will end up if you started with pyruvate being labeled at C1.

Answer 1

TCA Pathway

Isocitrate dehydrogenase , alpha-ketoglutarate dehydrogenase are decarboxylase enzyme

Redox reaction included:

Isocitrate ---- alpha-ketoglutarate

alpha-ketoglutarate-----Succinyl Co-A

Succinate----Fumerate

Malate----oxaloacetate

Substrate-level phosphorylation involves the reaction: Succinyl Co-A----Succinate (GTP/ATP formation)

• If carbonyl carbon of pyruvate is lablled as C14 and carbonyl carbon of oxaloacetate as C4 then CO₂is released at succinate dehydrogenase step.