Rapid Oxygen Uptake Research Articles

Endogenous respiration of yeast. I. The endogenous substrate

1. 1. Kinetic and chemical data suggest the presence of three endogenous substrates in a strain of Saccharomyces cerevisiae. These consist of two metabolically distinct glycogen pools and the disaccharide, trehalose. Lipides do not serve as a substrate for endogenous respiration. 2. 2. Utilization of one glycogen pool requires the presence of oxygen, while the other can be metabolized either aerobically or anaerobically. Trehalose is used only anaerobically. 3. 3. Anaerobically ethanol accumulates in amounts equal to the CO 2 produced. In addition, there is a slow anaerobic disappearance of the “oxidizable” glycogen pool with an equivalent accumulation of a TCA-soluble carbohydrate that is utilizable only aerobically. 4. 4. It is suggested that the rapid oxygen uptake observed after periods of anaerobiosis is due to oxidation of ethanol and the TCA-soluble carbohydrate and that the low R.Q.'s reported previously are the result of ethanol oxidation.

ON THE MECHANISM OF INDOLEACETIC ACID OXIDATION BY WHEAT LEAF ENZYMES

Partially purified enzyme preparations of wheat leaves oxidize indoleacetic acid completely in the presence of manganese and a monohydroxyphenol or resorcinol. A characteristic feature of the oxygen uptake is an induction period followed by a rapid oxygen uptake which ceases when 1 mole of oxygen is consumed per mole indoleacetic acid added. One mole of carbon dioxide is evolved per mole indoleacetic acid. There is no lag in carbon dioxide evolution, but it is not given off anaerobically. Oxygen, blue light, and acetaldehyde overcome the induction period. Hydrogen peroxide formed in a final aerobic dehydrogenase step is utilized to provide a source of manganic ions which act as an electron acceptor in an initial oxidative step.

On the oxygen uptake of Paracentrotus lividus egg homogenates after the addition of calcium

1. 1. After the addition of small amounts of calcium to Paracentrotus egg homogenates made from Ca-free egg-suspensions there is a sudden, very rapid oxygen uptake lasting about 20 minutes. The same phenomenon has previously been found in Psammechinus. 2. 2. Hypertonicity is so far the only model procedure for obtaining this same effect. The calcium and hypertonicity oxygen uptakes behave alike in all respects. They cannot be superimposed on one another. Evidently they are released over the same mechanisms. 3. 3. The sensitivity of the Paracentrotus egg homogenates to both calcium and hypertonicity disappears between 1−1 1 2 hours after homogenization (18 °C). 4. 4. The oxygen uptake investigated is not caused by an increased glycogen break-down. Carbohydrate metabolites are not involved, for the oxygen uptake is not linked to any carbon dioxide production. The oxidation energy cannot be used for esterification of phosphate. Within the limits of error no difference in the acid soluble phosphate fractions could be found during the initial 10 minutes of the calcium-produced oxygen uptake between calcium-free and calcium-treated homogenates. 5. 5. The oxygen uptake is not caused by an oxidation of diphosphopyridine nucleotide, for it is equally evident in the presence of pyocyanine. 6. 6. Monoiodoacetate inhibits the oxygen uptake. This fact is taken as evidence that the effect is due to or transmitted by substances containing sulfhydryl groups. By nitroprusside test a certain unmasking of sulfhydryl groups was indicated after the addition of calcium to homogenates. Some evidences have been collected in support of the hypothesis that under the direct or indirect influence of calcium protein-bound sulfhydryl groups are uncovered and oxidized.

THE OXYGEN CONSUMPTION OF THE MICROSPORES OF TRILLIUM IN RELATION TO THE MITOTIC CYCLE

The oxygen consumption of 265 single Trillium erectum anthers was measured before and during the mitotic cycle of the microspores using a modified differential microrespirometer. The results show a rising oxygen consumption of the anther in the premitotic stages followed by a sharp drop immediately preceding and during active division. It is suggested from these results that active division may be associated with anaerobic behavior and that the rapid uptake of molecular oxygen commonly associated with proliferating tissues is probably characteristic of premitotic development.