Activation of succinate dehydrogenase from adultFasciola hepatica(Trematoda)

Abstract

SummaryThe succinate dehydrogenase of adultFasciola hepaticawas 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 ofF. hepaticasuccinate 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 ofF. hepaticawas 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.