Respiratory Metabolism of Parasitic Helminths without Participation of the Cytochrome System

Abstract

LASER¹ has demonstrated high succinic dehydro-genase activity in extracts of muscle pulp of Ascaris lumbricoides. In the presence of succinate these preparations reduce methylene blue, but do not react with atmospheric oxygen. On the other hand, succinate stimulates the respiration of dialysed muscle mince of Ascaris². Furthermore, we have observed that homogenates of thoroughly washed Ascaris muscle oxidize succinate even in the absence of methylene blue. The activity of this preparation was markedly higher in 100 per cent oxygen than in air, and was increased when catalase and ethyl alcohol were added, indicating the production of hydrogen peroxide¹. No oxygen uptake was observed under similar conditions in the absence of succinate. Therefore, succinic dehydrogenase of Ascaris muscle can transfer hydrogen either to methylene blue or to an enzyme system, which, in turn, reacts with atmospheric oxygen. However, the latter is not identical with the cytochrome – cytochrome oxidase system considered to be the universal catalyst of all respiring cells³.