ENZYME LOCALIZATION IN THE ANAEROBIC MITOCHONDRIA OF ASCARIS LUMBRICOIDES

Abstract

Mitochondria from the muscle of the parasitic nematode Ascaris lumbricoides var. suum function anaerobically in electron transport-associated phosphorylations under physiological conditions. These helminth organelles have been fractionated into inner and outer membrane, matrix, and intermembrane space fractions. The distributions of enzyme systems were determined and compared with corresponding distributions reported in mammalian mitochondria. Succinate and pyruvate dehydrogenases as well as N A D H oxidase, Mg++-dependent ATPase, adenylate kinase, citrate synthase, and cytochrome c reductases were determined to be distributed as in mammalian mitochondria. In contrast with the mammalian systems, fumarase and NAD-linked "malic" enzyme were isolated primarily from the intermembrane space fraction of the worm mitochondria. These enzymes are required for the anaerobic energy-generating system in Ascaris and would be expected to give rise to N A D H in the intermembrane space. The need for and possible mechanism of a proton translocation system to obtain energy generation is suggested.

NADH→NAD+Transhydrogenation in AdultAscaris suumMitochondria

“…Consistent with the prior reports demonstrating a predominant, mitochondrial IM association of both NT and LD activities (Rew and Saz, 1974;Fioravanti and Saz, 1976;Kommuniecki and Saz, 1979), a predominant membrane association for both activities was apparent (Table I). Moreover, assessments of the fractionated mitochondria demonstrated a predominant membrane association of NADH dehydrogenase activity that was consistent with this activity reflecting the NADH dehydrogenase components of the cyto c R systems.…”

“…1) prompted a comparison of pH effects on yet another mitochondrial, NADH-utilizing activity of A. suum mitochondria, viz., NADH-cyto c R. As established previously, mitochondrial cyto c R activity in A. suum reflects both a rotenone-insensitive and rotenone-sensitive system associated with the outer membrane (OM) and IM, respectively (Rew and Saz, 1974). As presented in Figure 2, decreasing pH from 9.0 to 6.5 was accompanied by decreases in both cyto c RI and cyto c RS activities, with no significant differences between them.…”

“…However, K¨ohler (1977) subsequently reported that the mitochondrial IM of A. suum is impermeable to fumarate and that ''malic'' enzyme is equally distributed in the IMS and matrix compartments of A. suum. Nevertheless, compelling data support the notion that a mechanism(s) exists whereby reducing equivalents arising from NADH in the ascarid IMS can be translocated across the IM to reduce matrix NAD þ (Rew and Saz, 1974;Fioravanti and Saz, 1976;K¨ohler and Saz, 1976).…”

“…Previous studies indicated that both the ''malic'' enzyme and fumarase of adult A. suum are principally localized in the mitochondrial intermembrane space (IMS) (Rew and Saz, 1974). Thus, upon entering the mitochondrion, the ''malic'' enzyme-catalyzed decarboxylation of malate would result in NADH formation in the IMS.…”

Oxidation and reduction of cytochrome c by mitochondrial enzymes ofSetaria cervi

“…The presence of a similar type of reductase has been reported also in other helminths, e.g. Ascaris lumbricoides (Rew & Saz, 1974), Ascaris suum (Kikuchi, 1959), Setaria digitata (Raj et ah, 1988) and Hymenolepis diminuta (Younghee & Fioravanti, 1985).…”