Amino Acid Degradation

• the carbon skeletons of amino acids can provide some metabolic energy by feeding into the TCA cycle
• glucogenic vs. ketogenic amino acids

  • glucogenic = provide a net gain of glucose
  • ketogenic = no net gain in glucose
• Most amino acids are both ketogenic and glucogenic.
• Only leucine and lysine are only ketogenic.
• (add labels)

  A) PDH

  B) pyruvate carboxylase

  C) gluconeogenesis

  D) TCA

  
• transamination examples of amino acid to carbon molecule

  • alanine to pyruvate
  • aspartate to oxaloacetate
• glutamate dehydrogenase takes glutamate and forms alpha-ketoglutarate, using water and NAD+ in the process and releasing NADH, H+, and NH4+
• branched chain alpha-ketoacid dehydrogenase complex (BCKDH) = similarity to the pyruvate dehydrogenase (PDH) complex

  • three enzymes each with different cofactors
  • E1: uses TPP, which picks up the 2C chain
  • E2: uses lipoamide or lipoic acid that acts as swinging arm, pick up carbon from E1 and deliver to CoA to make acetyl-CoA
  • E3: re-oxidizes lipoamide in E2 using FAD to pick up electrons and FAD gets regenerated using NAD+