Biochemical Cytology of Trichomonad Flagellates. II. Subcellular Distribution of Oxidoreductases and Hydrolases in Monocercomonas sp.*

SYNOPSIS A primitive trichomonad, Monocercomonas sp. (strain NS‐1:PRR) from Natrix sipedon , was grown axenically in Diamond's medium. Activity of NADH oxidase, malate dehydrogenase, malate dehydrogenase (decarboxylating) and of the anaerobic enzymes, pyruvate synthase and hydrogenase as well as of several hydrolases was demonstrated in homogenates. The subcellular distribution of these activities was studied by means of analytical differential and isopycnic centrifugation of homogenates prepared in 0.25 M sucrose. NADH oxidase and malate dehydrogenase are in the nonsedimentable part of the cytoplasm. Malate dehydrogenase (decarboxylating), pyruvate synthase, and hydrogenase are associated with a large particle which equilibrates at density 1.22. In its properties, this particle corresponds to the microbody‐like hydrogenosomes of Tritrichomonas foetus. The 5 hydrolases studied are associated with at least 2 different particle populations: a large particle population equilibrating at densities from 1.10 to 1.16 is the exclusive location of 3 enzymes ( β ‐galactosidase, protease and β ‐N‐acetylglucosaminidase), 2 of which have a pH optimum close to neutrality. These particles contain part of the acid phosphatase and β ‐glucuronidase. Another part of these 2 enzymes is associated with a separate population of smaller granules with equilibrium densities of 1.16 to 1.18. The 2 types of hydrolase‐carrying particles are also biochemically very similar to their counterparts in T. foetus.