Oxidative activities in mitochondria-like particles from Setaria digitata, a filarial parasite

Abstract

The oxidative metabolic potential of Setaria digitata, a filarial parasite found in the intraperitoneal cavity of cattle, was investigated. These worms showed active wriggling movements which were not affected by respiratory poisons such as cyanide, rotenone and malonate. They also possessed cyanide-insensitive and glucose-independent oxygen consumption pathways. By differential centrifugation of sucrose homogenates, a fraction containing mitochondria-like particles was obtained in which the activity of the marker enzyme, succinate dehydrogenase, was recovered. This fraction catalysed succinate- and NADH-dependent reduction of both cytochrome c and dyes. Oxygen uptake found with succinate, NADH and ascorbate as substrates was not sensitive to cyanide. Cytochromes could not be detected in either this fraction or homogenates of the worms. H2O2 generation with a number of substrates and lipid peroxidation by measuring malondialdehyde formed as well as by accompanying oxygen uptake were demonstrated in the mitochondria-like particles. A lipid quinone, possibly with a short side chain and related to ubiquinone, was detected in the worms. The results suggested the existence of two cyanide-insensitive oxygen-consuming reactions in Setaria: one respiratory substrate-independent lipid peroxidation, and a second substrate-dependent reaction that requires an auto-oxidizable quinone but not a cytochrome system.

Biochemical composition and metabolic pathways of filarial worms Setaria cervi: search for new antifilarial agents

“…A lipid quinone, possibly with a short side-chain and related to ubiquinone, has been detected in adult worms. The results suggest the existence of two cyanide-insensitive oxygen-consuming reactions in Setaria ; one respiratory substrate-independent lipid peroxidation and a second substrate-dependent reaction that requires an auto-oxidizable quinone (Raj et al , 1989).…”

Setaria digitata in advancing our knowledge of human lymphatic filariasis

“…The activities of succinate dehydrogenase (SDH) and fumarate reductase (FR) exhibit a ratio of 1.75, a value characteristic of facultative anaerobes (Banu et al , 1991). Oxygen uptake assays and scoring of the wriggling rate of adult worms have been used to demonstrate that aerobic respiration is insensitive to the respiratory poison cyanide (Raj et al , 1988). This was evident by unchanged rates of oxygen uptake in the presence of cyanide, and by the absence of spectrophotometrically detected cytochrome oxidase – the enzyme inhibited by cyanide.…”