Biochemical Studies on the Muscle Microsomes of Ascaris lumbricoides var. suum

I. Biochemical Characterization and Electron Transport of Ascaris Microsomes

Abstract

Two subcellular fraction, P-1 and P-2, were isolated by differential centrifugation from 0.25M sucrose muscle homogenates of the parasitic roundworm, Ascaris lumbricoides suurn. Morphological studies indicated that P-1 fraction consisted of intact mitochondria, whereas P-2 fraction consisted almost exclusively of vesicular components.
The difference spectrum of Ascaris microsomes showed a characteristic b-type cytochrome spectrum with three distinct absorption peaks at 560, 525, and 424nm. However, the α-peak at 560nm was asymmetric with a shoulder at 555nm. This microsomal b-type cytochrome was reduced by NADH, which was inhibited by rotenone and HgCl₂. The reduced b-type cytochrome was easily reoxidized by shaking. NADH-oxidase activity observed in Ascaris microsomes was inhibited by rotenone, but not by KCN, NaN₃, and antimycin A. On the other hand, NADH-cytochrome c and NADH-neotetrazolium (NT) reductase activities in Ascaris microsomes were not inhibited by antimycin A and rotenone, but were inhibited by HgCl₂. Further observations indicated that neither HgCl₂ nor rotenone inhibited Ascaris microsomal NADH-ferricyanide (FC) reductase activity, but rabbit antibody prepared against the purified NADH-FC reductase inhibited the NADH-cytochrome c reductase activity, the reduction of b-type cytochrome and the NADH-oxidase activity, as well as microsomal NADH-FC reductase activity.