Activation of succinate dehydrogenase from adultFasciola hepatica(Trematoda)

Abstract

SummaryThe succinate dehydrogenase of adult Fasciola hepatica was found to exist in active and inactive forms. The enzyme was inactivated by 1 μM oxaloacetate and activated by incubation with compounds which bind to the active site (succinate, fumarate, malonate) or by incubation with anions and certain nucleotides. The activation of the enzyme by succinate followed first-order kinetics. The extent of activation of F. hepatica succinate dehydrogenase depended on the nature and concentration of the activator and on the pH. The rate of activation of the enzyme depended on the temperature. In contrast, the fumarate reductase activity of F. hepatica was not activated by incubation with substrate or anions and was not inhibited by oxaloacetate (100 μM). The significance of these results in the regulation of the tricarboxylic acid cycle in parasitic helminths is discussed.

Energy metabolism and its regulation in the adult liver flukeFasciola hepatica

“…These results, together with the presence of intermediates of the cycle (Bryant & Williams, 1962;Thorsell, 1963;Kurelec, 1964a, b) indicate that a functional cycle exists, but is probably of little physiological significance owing to the low activities of aconitase and isocitrate dehydrogenase. The principal function of these tricarboxylic acid cycle enzymes is the partial reversal of the cycle in CO 2 fixation, and in anabolic processes (Barrett, 1978).…”

“…It is activated by incubation with anions, nucleotides and compounds which bind to the active site. Fumarate reductase, on the other hand, has no known modulator, and activity is not affected by incubation with substrates, anions or oxaloacetate (Barrett, 1978).…”

The mode of action of some benzimidazole drugs onTrichinella spiralis

“…We consider that the diminution of SDH activity in the larvae probably reflects that the maintenance medium after 72 h of incubation is a less aerobic environment than the host muscle. In fact, the SDH/FR ratio, which is a good index of the metabolic condition of a tissue and is lower in anaerobic beings (Barrett, 1978), falls from l -90 to 1-15. On the other hand, depletion of glycogen reserves has been observed in other parasitic helminths when they are maintained in vitro (Wong & Fernando, 1970;Sangster & Prichard, 1984).…”

“…Larvae previously recovered from the liquid medium or from infested mice were washed and homogenized, and the mitochondrial fraction isolated from the homogenate by differential centrifugation. Succinate dehydrogenase (SDH, EC 1.3.99.1) and fumarate reductase (FR, EC 1.3.99.1) activities were determined essentially according to the method of Barrett (1978) and Prichard (1973), respectively. Further details have been given in a previous publication (Rodriguez Caabeiro et al 1985).…”

A comparative study of the succinate dehydrogenase–fumarate reductase complex in the genusTrichinella

“…Succinate dehydrogenase (SDH, EC 1.3.99.1) activity was determined by measuring the rate of oxidation of succinate to fumarate in the presence of 2,6-dichlorophenolindophenol at 600 nm, essentially according to the method of Barrett (1978). The final assay mixture contained : 0 1 M K-phosphate buffer (pH 76), 3 mM EDTA, 3 mM KCN, 01 mM 2, 6 dichlorophenolindophenol, 10 mM Na + succinate and the particulate fraction (approximately 100 fig protein).…”