Glyoxylate cycle




 Glyoxylate cycle

  • Glyoxylate cycle occurs in some microorganisms when acetate is sole source of carbon
  • This cycle has two unique enzyme- isocitrate lyase and malate synthase which bypass some of the reaction of TCA cycle.

figure: Glyoxylate cycle

  • Glyoxylate cycle is absent in higher organism.
  • At first acetylcoA is produced from acetate or by oxidation of higher fattyacids.
  • AcetylcoA then enter into TCA cycle and condensed with oxaloacetate to form citrate.
  • Citrate then isomerized to isocitrate.
  • Isocitrate lyase bypass the TCA cycle by splitting isocitrate into succinate and glycoxylate.
  • Succinate metabolized by TCA whereas Glycoxylate condenses with another molecule of acetylcoA to form malate in the presence of malate synthase.
  • Malate is converted into oxaloacetate by the enzyme malate dehydrogenase.

Significance of Glyoxylate cycle

  • It is bypass reaction of TCA cycle
  • It occurs in bacteria when they are cultured in acetate rich carbon source.
  • When Higher fattyacids are oxidized into acetylcoA without forming puruvate acids, then acetylcoA enters into glyoxylate cycle.

 Glyoxylate cycle