Question

Compare the Pyruvate Dehydrogenase Complex to the Branched Chain Ketoacid Dehydrogenase Complex. How are they similar and different in terms of functionality and nutrient requirements l. What organic acids are elevated when there is insufficient activity of the Pyruvate Dehydrogenase Complex (PDC) vs the Branched Chain Ketoacid Dehydrogenase Complex (BCKDC)? (Make sure to understand the difference between BKCDC and BCAA transaminase. These are two completely different enzymes in the BCAA degradation pathway) 1 point

Answer 1

1. Pyruvate dehydrogenase complex (PDC) is complex of three enzymes that converts pyruvate to acetyl- CoA in mitochondrial matrix in eukaryotes. Three enzymes include Pyruvate dehydrogenase (E₁), Dihydrolipoyl transacetylase (E₂), and Dihydrolipoyl dehydrogenase (E₃).
2. On the other hand, Branched-chain alpha-keto acid dehydrogenase complex (BCKDC) catalyzes irreversible catabolism of branched-chain amino acids L-isoleucine, L-valine, and L-leucine at mitochodrial inner membrane in animals. It helps in synthesis of long chain fatty acids by catalyzing L-isoleucine in bacteria. Like PDC, BCKDC also consists of three catalytical components; alpha-ketoacid dehydrogenase (E₁), dihydrolipoyl transacylase (E₂), and dihydrolipoamide dehydrogenase (E₃).
3. While the PDC depends on product of glycolysis to function and thus effectively depending on glucose, BCKDC functions on availability of branched amino acids.
4. Pyruvate dehydrogenase deficiency is reported to be responsible for hyper build up of lactic acid and pyruvate in body. This leads to lactic acidosis. Deficiancy in any of BCKDC enzymes is shown to be associated with build of branched-chain amino acids. Pathological condition like maple syrup urine disease is known to be caused in such conditions.
5. Unlike BCKDC, BCAA transaminase (BCAT) catalyse first step of branched chain amino acid degradation pathway. These exhibit reversible transaminase activity on branched chain amino acids and mark them for oxidative decarboxylation.