Carbohydrate and energy metabolism in trypanosome and plasmodia
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Carbohydrate and energy metabolism in trypanosome and plasmodia

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Carbohydrate and energy metabolism in trypanosome and plasmodia Carbohydrate and energy metabolism in trypanosome and plasmodia Presentation Transcript

  • CARBOHYDRATE AND ENERGY METABOLISM IN TRYPANOSOME AND PLASMODIA BY ASARE, KUMI KWAME
  • TRYPANOSOMES Trypanosomes go through a complex life cycle involving vertebrate host and a vector tsetse fly. Vertebrate host comprising long slender, intermediate and short stumpy form. Vector phase comprising procyclic trypomastigote, epimestigote and metacyclic form.
  • T. brucei actively catabolize glucose, fructose, mannose and glycerol. Long slender form lack mitochondral TCA and functional respiratory chain. Short stumpy stages is able to utilize alpha ketoglutarate, glucose, fructose and glycerol. Blood stream form do not store energy reserves. View slide
  • AEROBIC CONDITION The long slender forms metabolize glucose to pyruvate with trace amount CO2 and sometimes glycerol. Lack lactate dehydrogenase, pyruvate decarboxylase. Short stumpy form contain mitochondra and produce pyruvate, glycerol, acetate, succinate and co2 . Reoxidation of NADH in the glycosome is mediated G3P-DHAP. View slide
  • NAD-linked glycerol-3-phosphate dehydrogenase and mitochondrial FAD-linked glycerol-3-phosphate dehydrogenase-oxidase complex. The terminal oxidase reduce molecular oxygen to water
  • ANAEROBIC CONDITION Mitochondrial glycerol-3-phosphate oxidase is inhibited with salicyl hydroxamic acid (SHAM). Long slender forms continue to utilize glucose by G3P-DHAP which prevent glycerol-3-phosphate. Glycosomal ATP is trapped by the phosphorylation of glucose. Anaerobiosis leads to high glycerol-3-phosphate and ADP with decrease ATP cause glycerol-3- phosphate to diffuse out.
  • Causing reversal of glycerol kinase action to form ATP from glycerol-3-phosphate and ADP. In anaerobic condition glucose form equimolar amounts of pyruvate and glycerol with a net ATP of 1. Cells survive and remain motile under anaerobic condition with decrease ATP. Glycerol can not serve as substrate because G3P can not be oxidized to DHAP without molecular oxygen.
  • VECTOR STAGE Procyclic form metabolize glucose, fructose, mannose and glycerol to produce acetate, succinate, alanine, alpha ketoglutarate and CO2. Under anaerobic condition utilize glucose and glycerol and produce CO2 in a form of succinate and acetate. Glycosomal phosphoenolpyruvate carboxykinase and malate dehydrogenase is present in procyclic forms.
  • DIAGRAM
  • THE PLASMODIA Erythrocytic stages of the malaria parasite do not reserve carbohydrates. Utilization of glucose increase to about 50-100 folds. In infected red cells with P. falciparum utilize glucose in anaerobic glycolysis to lactic acid. Both the parasite and the host lack TCA cycle. However, Avian malaria parasite under TCA cycle with the presence of enzymes isocitrate dehydrogenase and succinate dehydrogenase.
  • There is the presence malate dehydrogenase in both mammalian parasite and avian parasite but appears to cytosolic. Although intraerythrocytic stages depend mainly on glycolysis but mitochondria function influence the parasite survival. They are capable of oxidizing NADH, glycerol- 3-phosphate and succinate.
  • Mitochondria of P. falciparum oxidize glutamate. NADH-fumarate reductase involved in the reoxidation of mitochondrial NADH. P. falciparum has a complete set of glycolytic enzyme which is high in the infected cells.
  • Several non-glycolytic enzymes such as glucose-6-phosphate dehydrogenase, diphosphoglycerate mutase and adenylate kinase decreased in activity. Most of the enzymes except for glucose-6- phosphate dehydrogenase can be obtain from the parasite after lysis. The pathway for the synthesis of 2,3- diphosphoglycerate is absent.