The role of amino acids in the energy generating pathways of Litomosoides carinii

Kelvin Davies, Peter Köhler

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The filarial parasite Litomosoides carinii was able to survive for longer than 15 h in basic filarial medium (BFM) containing either glutamine or alanine as a sole substrate. The filariids were more motile in BFM containing glucose, but even higher motility was recorded in media containing both glucose and glutamine. Incubations under aerobic conditions showed that radiolabelled glutamine was metabolised primarily to CO2. In addition, small amounts of lactate and acetate were excreted in almost equimolar quantities. Incubations where both glutamine and glucose were present demonstrated that the glutamine carbon utilised by the parasite could be completely recovered in the above three end products. The glutamine nitrogen could be recovered in the additional excretory products, alanine and ammonia. The glutamine-dependent viability of L. carinii was affected by known inhibitors of the mitochondrial respiratory chain. Glucose utilisation, and the production of CO2 from this substrate, were greatly stimulated by the presence of glutamine in the external medium. Various carbon balance studies, in conjunction with enzymatic analyses, suggest that in L. carinii, glutamine provides an input of carbon into the tricarboxylic acid (TCA) cycle, probably at the level of α-ketoglutarate. This increased availability of Krebs cycle intermediates will stimulate the rate of pyruvate oxidation via acetyl-CoA and the TCA cycle, and thus increase the rate of carbon flux through glycolysis. The energetic advantage associated with the utilisation of the glucose/glutamine substrate couple may explain the worm's enhanced motor activity compared to incubations with glucose as the sole energy source. Alanine was found to be degraded by the filariid to equivalent amounts of lactate, acetate and CO2, indicating a relatively low energetic efficiency. There was no detectable uptake of glutamate. A variety of other amino acids tested were neither metabolised nor able to maintain worm viability in vitro.

Original languageEnglish (US)
Pages (from-to)115-124
Number of pages10
JournalMolecular and Biochemical Parasitology
Volume41
Issue number1
DOIs
StatePublished - 1990
Externally publishedYes

Fingerprint

Filarioidea
Glutamine
Amino Acids
Glucose
Citric Acid Cycle
Alanine
Carbon
Lactic Acid
Parasites
Acetates
Carbon Cycle
Acetyl Coenzyme A
Glycolysis
Electron Transport
Pyruvic Acid
Ammonia
Glutamic Acid
Motor Activity
Nitrogen

Keywords

  • Alanine
  • Glucose
  • Glutamine
  • Litomosoides carinii
  • Metabolism
  • Tricarboxylic acid cycle

ASJC Scopus subject areas

  • Molecular Biology
  • Parasitology

Cite this

The role of amino acids in the energy generating pathways of Litomosoides carinii. / Davies, Kelvin; Köhler, Peter.

In: Molecular and Biochemical Parasitology, Vol. 41, No. 1, 1990, p. 115-124.

Research output: Contribution to journalArticle

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abstract = "The filarial parasite Litomosoides carinii was able to survive for longer than 15 h in basic filarial medium (BFM) containing either glutamine or alanine as a sole substrate. The filariids were more motile in BFM containing glucose, but even higher motility was recorded in media containing both glucose and glutamine. Incubations under aerobic conditions showed that radiolabelled glutamine was metabolised primarily to CO2. In addition, small amounts of lactate and acetate were excreted in almost equimolar quantities. Incubations where both glutamine and glucose were present demonstrated that the glutamine carbon utilised by the parasite could be completely recovered in the above three end products. The glutamine nitrogen could be recovered in the additional excretory products, alanine and ammonia. The glutamine-dependent viability of L. carinii was affected by known inhibitors of the mitochondrial respiratory chain. Glucose utilisation, and the production of CO2 from this substrate, were greatly stimulated by the presence of glutamine in the external medium. Various carbon balance studies, in conjunction with enzymatic analyses, suggest that in L. carinii, glutamine provides an input of carbon into the tricarboxylic acid (TCA) cycle, probably at the level of α-ketoglutarate. This increased availability of Krebs cycle intermediates will stimulate the rate of pyruvate oxidation via acetyl-CoA and the TCA cycle, and thus increase the rate of carbon flux through glycolysis. The energetic advantage associated with the utilisation of the glucose/glutamine substrate couple may explain the worm's enhanced motor activity compared to incubations with glucose as the sole energy source. Alanine was found to be degraded by the filariid to equivalent amounts of lactate, acetate and CO2, indicating a relatively low energetic efficiency. There was no detectable uptake of glutamate. A variety of other amino acids tested were neither metabolised nor able to maintain worm viability in vitro.",
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