Ref ID : 4020
Dipak B. Datta and Joseph S. Kahn; Some Biochemial Properties of Mitochondria Isolated from Euglena gracilis. J.Protozool. 24(1):187-192, 1977
Reprint
In File
Notes
Mitochondria were isolated from Euglena gracilis strain Z by pressure-breakage of the cells and sucrose-cushion centrifugation. Multiple peaks (2-4) were observed in the rate of phosphorylation with Mg-ADP-phosphate concentration curves. The phosphorylative and oxidative activities were highest with NADH as the substrate, moderate with succinate, and lowest with glutamate. Inhibition of phosphorylation with 2,4-dinitrophenol and carbonyl cyanide, m-chlorophenylhydrazone gave sigmoidal concentration curves, with the extent of inhibition by DNP depending on the substrate used. Inhibition of phosphorylation by valinomycin, atractyloside, or carboxyatractyloside was only ~60%. Oligomycin inhibited phosphorylation in 2 phases at low and high concentrations; it inhibited Mg-ATPase in a sigmoidal fashion. Both phosphorylation and oxidation had discontinuities in Arrhenius plots at 34 degrees C and 18 degrees C. The relative Mg2+ -dependent nucleoside triphosphatase activity was: 1 for ATP and GTP, 0.6 for ITP, 0.15 for CTP and UTP; with Ca2+ in place of Mg2+ this activity was 0.35. Both DNP and CCCP stimulated that Mg-ATPase 50-200%. The optimal pH for the stimulation was ~7 regardless of the uncoupler used, and ~8 without the uncouplers. The few differences observed between mitochondrial from Euglena and those from other sources are probably due to the fragmentation of the reticular mitochondrial structure during isolation and not to unique characteristics of these mitochondria.