Strongyloides ratti: Mitochondrial enzyme activities of the classical electron transport pathway in the infective (L3) larvae

Abstract

Submitochondrial particles prepared from S. ratti L3 larvae exhibited NADH-oxidase (NOX), NADH-ferricyanide reductase (NFR), NADH-cytochrome- c-reductase (NCR), succinate-cytochrome- c-reductase (SCR), and cytochrome- aa 3 -oxidase activities of 2.1 ± 0.3, 8.9 ± 1.3, 0.6 ± 0.1, 1.0 ± 0.2 and 1.2 ± 0.3 nm min −1 mg protein −1 respectively, at 37°C. The NCR and NOX activities were 39.3% and 23.5% of the NFR activity, suggesting the occurrence of a rate-limiting step or bifurcation of the respiratory electron transport (RET) pathway on the oxygen-side of RET-Complex I. The NCR activity was 50% that of cytochrome- aa 3 -oxidase activity which suggests partitioning of electron flow at the level of RET-Complex III and/or the quinone-function. Antimycin A and rotesone but not 2-thenoyl trifluoreacetone (TTFA) inhibited NCR activity, the EC 50 values were 3.6 × 10 −6 m, 3.7 × 10 −7 m, respectively. SCR activity was inhibited by antimycin A (EC 50 = 3.8 × 10 −6 m) and TTFA (EC 50 = 2.8 × 10 −5 m) but not by rotenone. The results suggest that presence of classical and alternate RET-pathways in S. ratti L3 larvae.