Phosphoenolpyruvate metabolism in Teladorsagia circumcincta: a critical junction between aerobic and anaerobic metabolism.
Nematodes which have adapted to an anaerobic lifestyle in their adult stages oxidise phosphoenolpyruvate (PEP) to oxaloacetate rather than pyruvate as the final product of glycolysis. This adaptation involves selective expression of the enzyme phosphoenolpyruvate carboxykinase (PEPCK), instead of pyruvate kinase (PK). However, such adaptation is not absolute in aerobic nematode species. We have examined the activity and kinetics of PEPCK and PK in larvae (L(3)) and adults of Teladorsagia circumcincta, a parasite known to exhibit oxygen uptake. Results revealed that PK and PEPCK activity existed in both L(3)s and adults. The enzymes had differing affinity for nucleotide diphosphates: while both can utilise GDP, only PK utilised ADP and only PEPCK utilised IDP. In both life cycle stages, enzymes showed similar affinity for PEP. PK activity was predominant in both stages, although activity of this enzyme was lower in adults. When combined, both the activity levels and the enzyme kinetics showed that pyruvate production is probably favoured in both L(3) and adult stages of T. circumcincta and suggest that metabolism of PEP to oxaloacetate is a minor metabolic pathway in this species.
Institute of Food Nutrition and Human Health, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand. D.C.simcock@massey.ac.nz
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Simcock
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Walker
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Pedley
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Simpson
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Brown
D000018:Abomasum / Q000469:parasitology; D000244:Adenosine Diphosphate / Q000378:metabolism; D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D005260:Female; D006153:Guanosine Diphosphate / Q000378:metabolism; D007290:Inosine Diphosphate / Q000378:metabolism; D007700:Kinetics; D007814:Larva / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D062907:Oxaloacetic Acid / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D010728:Phosphoenolpyruvate / Q000378:metabolism*; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000378:metabolism*; D019289:Pyruvic Acid / Q000378:metabolism; D012756:Sheep; D012757:Sheep Diseases / Q000469:parasitology; D014251:Trichostrongyloidea / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D014252:Trichostrongyloidiasis / Q000469:parasitology / Q000662:veterinary
D006153:Guanosine Diphosphate; D062907:Oxaloacetic Acid; D000244:Adenosine Diphosphate; D010728:Phosphoenolpyruvate; D019289:Pyruvic Acid; D007290:Inosine Diphosphate; D008291:Malate Dehydrogenase; D011770:Pyruvate Kinase; D019764:Phosphoenolpyruvate Carboxykinase (ATP)