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Glucogenic and ketogenic amino acids


Amino acids can be classified as being “glucogenic” or “ketogenic” based on the type of intermediates that are formed during their breakdown or catabolism. The catabolism of glucogenic amino acids produces either pyruvate or one of the intermediates in the Krebs Cycle. The catabolism of ketogenic amino acids produces acetyl CoA or acetoacetyl CoA (see Figure 1).
Figure 1. Glucogenic amino acids are listed in GREEN boxes and ketogenic amino acids are listed in YELLOW boxes.
There is a rare medical condition in which a person is deficient in the pyruvate dehydrogenase enzyme that converts pyruvate to acetyl CoA – a precursor for the Krebs Cycle. Signs and symptoms vary, but there are generally two main manifestations. First, patients can have an elevated blood lactate (lactic acid) level. Second, patients may have neurological defects, including microcephaly (a small head circumference) and/or mental retardation. Treatment is currently limited and not very effective. Moreover, damage to the brain is often irreversible.
Your biochemistry study partner looks at Figure 1 and exclaims, “This doesn’t make sense - why can’t acetyl-coA and the ketogenic amino acids be converted back to pyruvate to create glucose using pyruvate dehydrogenase?” With your knowledge of basic chemistry, you answer:
Choose 1 answer: