Two types of pyruvate kinase in schistosomes and filariae.

-1 . Pyruvate kinase (PK) from the trematode Schistosoma mansoni closely resembles PK from rabbit muscle in its response to various purine and pyrimidine nucleoside diphosphates and divalent cations, in its insensitivity to activation by FDP and relative insensitivity to inhibition by ATP and in its somewhat higher affinity for PEP. 2. PK's from the filarial nematodes Litomosoides carinii and Dirofilaria immitis closely resemble PK from rabbit liver in the pattern of their substrate and cofactor specificities, by being strongly activated by FDP and inhibited by ATP, and by showing a relatively lower affinity for PEP. 3. The properties of PK from S. mansoni miracidia were indistinguishable from those of PK from the adult forms, and this was also the case for the PK's from D. immitis microfilariae and adults. 4. The molecular weights of PK's from S. raansoni, D. immitis and rabbit muscle were all around 270,000 _.+ 10 per cent. INTRODUCTION PARASITIC helminths have been found incapable of completely oxidizing glucose, whatever their habitat or degree of dependence upon molecular oxygen (Saz, 1970). The predominant end products of their carbohydrate metabolism are generally succinate or derivatives thereof, acetate and lactate, but the output of these fermentation products can vary widely among the genera of cestodes, trematodes and nematodes (Saz & Bueding, 1966). Bueding & Saz (1968) called attention to the positive correlation between the PK~f activities of helminths and the predominance of lactate as a fermentation end product. However, they also pointed out that this ostensibly straightforward * This investigation was supported by the United States--Japan Co-operative Medical Science Program administered by the National Institute of Allergy and Infectious Diseases, N.I.H., Department of Health, Education and Welfare. t The following abbreviations are employed: PEP, phosphoenolpyruvate; OAA, oxaloacetate ; FDP, fructose 1,6-diphosphate; PK, pyruvate kinase; LDH, lactate dehydrogenase; MDH, malate dehydrogenase; NAD and NADH, nicotinamide adenine dinucleotide and its reduced form; AMP, adenosine monophosphate; ADP, adenosine diphosphate; ATP, adenosine triphosphate; IDP, inosine diphosphate; GDP, guanosine diphosphate; UDP, uridine diphosphate; CDP, cytidine diphosphate; dADP, deoxyadenosine diphosphate.