INTERMEDIARY METABOLISM OF LIVER FLUKE FASCIOLA HEPATICA .I. BIOSYNTHESIS OF PROPIONIC ACID

A carbon balance study of the liver fluke Fasciola hepatica was made for the purpose of comparing its excretion of volatile fatty acids with its glucose consumption. The presence of all intermediates of the citric acid cycle under aerobic conditions was demonstrated by means of paper chromatography. The amounts of acetic acid, propionic acid, lactic acid, succinic acid and carbon dioxide formed were measured. In addition to these acids, the excretion of methylmalonate was demonstrated. Under anaerobic conditions using NaH14C03, the parasite exhibits phosphopyruvate carboxylase activity leading to succinate formation. The succinate dehydrogenase activity was compared with that of rat liver by measuring the V of the enzyme in both directions. The rate of fumarate reduction was found to be much higher than in rat liver. The presence of methylmalonyl-CoA mutase and propionyl-CoA carboxylase in Fasciola hepatica explains the excretion of propionate from succinate via succinyl-CoA, methylmalonyl-CoA, propionyl-CoA and propionate. As a result of these studies a tentative diagram of the intermediary metabolism of Fasciola hepatica is proposed. © 1969, IEEE. All rights reserved.