CHARACTERIZATION OF HYDROGENOSOMES AND THEIR ROLE IN GLUCOSE-METABOLISM OF NEOCALLIMASTIX SP L2

In the anaerobic fungus Neocallimastix. sp. L2 fermentation of glucose proceeds via the Embden-Meyerhof-Parnas pathway. Enzyme activities le ading to the formation of succinate, lactate, ethanol, and formate are associated with the cytoplasmic fraction. The enzymes 'malic enzyme', NAD(P)H:ferredoxin oxidoreductase; pyruvate : ferredoxin oxidoreducta se, hydrogenase, acetate: succinate CoA transferase and succinate thio kinase leading to the formation of H-2, CO2, acetate, and ATP are loca lized in microbodies. Thus, these organelles are identified as hydroge nosomes. In addition, the microbodies contain the O2-scavenging enzyme s NADH- and NADPH oxidase, while NAD(P)H peroxidase, catalase, or supe roxide dismutase could not be detected. In cell-free extracts from zoo spores of Neocallimastix sp. L2 the specific activities of hydrogenoso mal enzymes as well as the quantities of these proteins are 2- to 6-fo ld higher than in mycelium extracts. These findings suggest that hydro genosomes perform an important role - especially in zoospores - as H-2 -evolving, ATP-generating and O2-scavenging organelles.