Some Biochemical Properties of Mitochondria Isolated from Euglena gracilis*

SYNOPSIS. 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 C and 18 C. The relative Mg²⁺-dependent nucleoside triphosphatase activity was: 1 for ATP and GTP, 0.6 for ITP, 0.15 for CTP and and UTP; with Ca²⁺ in place of Mg²⁺ this activity was 0.35. Both DNP and CCCP stimulated the 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 mitochondria 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.     

Effect of Maltol on the Oxidation of DL-DOPA,Dopamine, N-Acetyldopamine (NADA), and Norepinephrine by Mushroom Tyrosinase

Maltol (3-hydroxy-2-methyl-4H-pyran-4-one) appears to inhibit the rate of oxidation of DL-DOPA, dopamine, NADA and epinephrine by tyrosinase when assayed spectropho-tometrically but not when assayed polarographically. Maltol has an effect on the spectrum of product(s) formed when each catecholamine was oxidized by tyrosinase showing that maltol hastens the disappearance of the quinones, possibly by conjugating with them. Indeed, at relatively high concentrations, maltol prevented the conversion of DL-DOPA, dopamine, and norepinephrine to their corresponding melanins via tyrosinase.     

The Occurrence, Growth-Temperature Relations and Nuclear Cytology of Protostelium mycophaga Olive and Stoianovitch

SYNOPSIS. Protostelium mycophaga Olive and Stoianovitch was isolated from 7 of 19 plant sources collected in a 15-mile radius of Syracuse, New York. Two of these isolations were made from up-right, nondecomposed plants. Spore diameter measurements of 4 of the isolates gave values that agree with those published for this species. The optimum temperature for the growth of P. mycophaga on enriched corn meal agar and Rhodotorula mucilaginosa was 20 C. Limited growth occurred at 10 C and no growth was observed above 30 C.
Mitosis is described from observations on living and stained preparations.