Glycolysis and related phosphorus metabolism in parasitic nematodes

Abstract

1. The r.q. of wholeNeoaplectana glaserirose from 0·56 to 1·10 when glucose was added to the medium. TheQ_o2was only slightly affected. Respiration of other nematode parasites was largely unaffected by exogenous glucose. Pyruvate had little or no effect.2. Inorganic phosphate increased whenAscaris lumbricoidesmuscle brei was incubated. In the presence of fluoride, or when aqueous extracts were used, easily and difficultly hydrolysable phosphate was formed. Phosphatase activity was dominant even in aqueous extracts ofA. lumbricoidesintestinal tissues and fluoride inhibited P_oformation only slightly. P_tot., and P_resIdualfell markedly in wholeA. lumbricoideswhich had been incubated anaerobically. Under aerobic conditions P_ofell slightly, but the other components rose considerably. Phosphorylative activity ofA. lumbricoidesovary was greater than in the muscle. Phosphorus compounds in perienteric fluid did not change during incubation.3. The breakdown of glycogen and the formation of glucose in aqueous extracts ofAscaridia galliwas inhibited by fluoride and phloridzin. Polysaccharide was synthesized in fluoride-poisoned preparations when glucose 1-phosphate was added. Polysaccharide formation inAscaris lumbricoidesfluoridepoisoned muscle preparations was demonstrated without the addition of Cori ester.4. Fructose 1:6-diphosphate added to aqueous extracts ofAscaridia galliandNematodirusspp. was rapidly metabolized at pH 6·5. At pH 7·2 the fructose content increased.5. In aqueous extracts ofNematodirusorAscaridiabrei which had been autolysed for short periods, 55–60% of the glycogen utilized appeared as glucose. Only small amounts of lactate were formed. Aqueous extracts ofNematodirusandAscaridiabrei which had been autolysed for long periods formed glucose in excess of the glycogen disappearing. When perienteric fluid, which contained amylase, was removed fromA. gallibefore autolysis, the amount of glucose formed was very much reduced. It is suggested that the excess glucose was formed from dextrins which were not estimated as glycogen and which were hydrolysed by perienteric fluid amylase during incubation.Lactate decreased during the incubation of extracts prepared from brei which had been autolysed for long periods.6. Bicarbonate decreased during the anaerobic incubation of aqueous extracts ofNematodirusspp. andAscaridia galliwhich were buffered with CO₂-bicarbonate. The decrease in bicarbonate was in excess of the CO₂expelled from the medium by acid formation.7. The acid-soluble phosphorus compounds of the different tissues ofAscaris lumbricoideswere examined. Compounds similar to a.t.p. were found in the intestine, ovary, muscle and possibly also in the perienteric fluid. The acid-unstable phosphorus compounds did not appear to be either creatine- or arginine-phosphate. Compounds similar to Embden ester were found in the ovary and muscle. The occurrence of the phosphate compounds found in the parasite is compared with figures given for other organisms.8. It is concluded that carbohydrate fermentation as far as lactate in nematode parasites was similar to that found in yeast and mammalian muscle. Energy was transferred by means of high-energy phosphate bonds.9. Phospholipids, which were found in considerable amounts in the tissues ofA. lumbricoides, were estimated as lecithin, sphingomyelin and serine- and ethanolamine-containing phospholipids. The amounts of the phospholipids found in the parasite tissues are compared with figures given for other organisms.The authors are deeply indebted to Prof. D. Keilin and Dr T. Mann of the Molteno Institute, Cambridge, for their advice and critical reading of the manuscript. Thanks are also due to Dr E. F. Gale and Dr E. Friedemann for advice on analytical procedures.