Anaerobic Yeast Research Articles

COMPARISON OF THE EFFECTS OF ULTRAVIOLET RADIATION ON THE INTRACELLULAR CATALASE OF AEROBIC AND ANAEROBIC YEAST

Abstract— Suspensioris of aerobic and anaerobic yeast were subjected to ultraviolet radiation (principally 254 mµ) under closely comparable experimental conditions, and changes in the level and in the temperature dependence of their catalase activity were determined. Qualita tively, the effects of U.V. on the enzyme of the anaerobic cells were similar to those on that of the aerobic cells. The effect of U.V. on the anaerobic catalase differed from that on the aerobic enzyme in the following respects: I, a considerably greater dose of U.V. was necessary in order to attain the maximum activity and the minimum activation energy of the enzyme‐substrate system; 2, a far greater dose was required before appreciable photoinactivation of the maxi mally active enzyme occurred; 3, photoinactivation proceeded at less than one‐half the rate; 4, the u.v.‐induced increase in the catalase activity of the suspension was virtually complete before appreciable reduction in activation energy occured. The first three of these differences were interpreted in terms of a model, which pictures the anaerohic catalase as being tightly bound to an intracellular chromophore group.

Potentiel d'oxydoréduction de la d-2-hydroxyacide: (accepteur) oxydoréductase de la levure anaérobie

The difference spectrum of oxidized enzyme minus d-lactate-reduced enzyme reveals the characteristic absorption bands of an oxidized flavin bound to the protein. The wavelengths of the peaks are: 455 mμ and 385 mμ. The oxidation-reduction potential of the FAD bound to the d-lactate dehydrogenase ( d-2-hydroxyacid: (acceptor) oxydoreductase) of anaerobic yeast has been determined. A spectrophotometric study of the equilibrium between the flavin group and the d-lactate-pyruvate system gives values of E mF = −0.178 Volt at pH7.0 and 30°. The pH-dependence coefficient of this potential is ΔE mF/ ΔpH = −0.03 V.

D-lactic dehydrogenase from anaerobic yeast: Reversible dissociation of fad and Zn by acid treatment of the holoenzyme

D-lactic dehydrogenase from anaerobic yeast: Reversible dissociation of fad and Zn by acid treatment of the holoenzyme

D-Lacticodéshydrogénase de la levure anaérobie etude de l'inactivation irréversible par un chélateur

The kinetics of inactivation by Versene of d-lactate dehydrogenase from anaerobic yeast was studied. Inactivation is irreversible: a diminution of free Versene concentration down to 10 −14 M does not lead to any reactivation. The initial velocity of inactivation is proportional to Versene concentrations and to enzyme concentrations. The Michaelis constant (in the reaction d-lactate to pyruvate) of the partially inactivated enzyme is not modified. Activation energy of inactivation is low (⩽ 3kcal/mole). d-Lactate (but not l-) protects the enzyme from inactivation by decreasing the velocity of inactivation. Neither the acceptors nor flavine-adenine dinucleotide protect. Variation of initial inactivation velocity in relation to d-lactate concentration during the inactivation follows a hyperbolic kinetics: d-lactate concentration giving half protection is 7 · 10 −6 M, that is 300 times smaller than the Michaelis constant. Inactivation of d-lactate dehydrogenase by Versene is therefore due to the loss of a metal ion that is necessary for enzyme activity. A hypothesis is advanced that the fixation of the substrate takes place in the vicinity of the metal.

D-lacticodehydrogenase from anaerobic yeast: Combination of apoenzyme with zinc and cobalt and comparison of reconstituted enzymes

D-lacticodehydrogenase from anaerobic yeast: Combination of apoenzyme with zinc and cobalt and comparison of reconstituted enzymes

On the nature of the block in the succinic oxidase system of anaerobically grown yeast

1. 1. The apparent absence of succinic dehydrogenase activity in anaerobically grown yeast, reported in the literature, was due to the employment of assay methods unsuitable for the measurement of the activity of this enzyme. With the aid of phenazine methosulfate, a reagent capable of reacting directly with the primary dehydrogenase, it has been shown that anaerobic yeast contains a high level of succinic dehydrogenase. 2. 2. Slonimski's observation of the virtual absence of succinic-cytochrome c reductase in anaerobically grown cells has been confirmed. 3. 3. During oxygenation of anaerobically grown cells a rapid, induced synthesis of the succinic-cytochrome activity occurs, which may be accompanied by a moderate increase in dehydrogenase activity. At the end of O 2 adaptation the ratio of succinic dehydrogenase to succinic-cytochrome c reductase activities is the same as in aerobically grown cells. 4. 4. The virtual absence of succinic oxidase in anaerobically grown cells is thus entirely due to the absence of the electron-transport system and not that of the dehydrogenase. O 2 adaptation thus entails synthesis of the hemoproteins and the incorporation of succinic dehydrogenase in the respiratory chain. 5. 5. The possible relevance of these observations to the apparent absence of other cytochrome-reducing dehydrogenases in anaerobic yeast has been pointed out.

The effect of prior growth conditions on the kinetics of adaptive enzyme formation in yeast

1. 1. The aeration of anaerobically grown yeast in a glucose-buffer solution induces the synthesis of two enzymes generally associated with mitochondria, the succinic dehydrogenase complex and cytochrome oxidase. 2. 2. Depending on how the anaerobic yeast was grown, both enzymes increase rapidly in a straight line from 0 time, or they exhibit a lag and an initial slow increase following an S-shaped curve. 3. 3. S-shaped adaptation curves for the succinic dehydrogenase complex were obtained with anaerobic yeast grown without shaking in a medium unsupplemented as to fats. 4. 4. Rapid straight-line synthesis of the succinic dehydrogenase complex was obtained with anaerobic yeast grown to completion of growth in an improved medium containing ergosterol, oleic acid and a higher sugar content. When the anaerobic yeast was grown in the improved medium, but was harvested earlier in the growth cycle, intermediate rates of adaptation were obtained. 5. 5. The possibility of fat deficiency in the anaerobically grown cells being a factor in the delay in enzyme formation is discussed and also the relation of these findings to the interpretations of the kinetics of adaptive enzyme formation and the mechanism of enzyme adaptation.

Glucosone: II. Inhibition of yeast metabolism, yeast hexokinase activity and tissue glycolysis

d-Glucosone inhibition of anaerobic yeast fermentation has been found to vary in degree with different yeast samples and to be somewhat dependent on the acidity of the medium. Glucosone did not affect the respiration of yeast but affected aerobic fermentation to about the same extent as it did anaerobic fermentation. The fermentation of fructose was inhibited by lower concentrations of glucosone than was the fermentation of glucose. Glucosone was found to inhibit phosphorylation by yeast hexokinase more than fermentation by whole yeast with either glucose of fructose as substrate. The phosphorylation of fructose was inhibited to a greater extent than was the phosphorylation of glucose. The inhibition was found to be competitive in nature and the enzyme-inhibitor dissociation constant was calculated to be of the order of 6.0·10 −5 M with either glucose or fructose as substrate. Glucosone has also been found to be inhibitory to the glycolysis of tumor- and brain-tissue slices. Much lower concentrations of glucosone were required for inhibition of tissue glycolysis than for inhibition of yeast fermentation. Brain tissue was more sensitive to glucosone than was tumor tissue.

EFFECT OF FUNGI ON THE OXIDATION‐REDUCTION POTENTIALS OF LIQUID CULTURE MEDIA

BIOLOGICAL OXIDATIONS and reductions which deal with tlle energy relationships essential to all forms of life have been studied by many investigators, all aiming at an ultimate understanding of these complex processes. Since the release or building up of energy involves the transfer of electrons, it is possible to measure these phenomena in biological systems by oxidation-reduction indicators or electrical apparatus in which electron transfers result in color changes or in the building up of an electrical charge at suitable electrodes. Investigations on the effects of plants on oxidationreductioln potentials (Eh) have been confined chiefly to bacteria and yeasts. Hewitt (1933) has given an extensive review of the effects of bacteria on electrode potentials, listing over 65 references dealing with this suibject. Many. more results have been reported on oxidation-reduction phenomena in relation to bacterial metabolism since Hewitt's report was published. Potter (1912) showed that yeast cells produced redulcing conditions in their surrounding medium. Using both indicators and electrical methods of measuring Elh, Cannan, Cohen, and Clark (1926) followed the potential changes produced by yeast cells suspended in buffer solutions. They concluded that yeast cells produce hydrogen donators which reduce tthe media and result in the lowering of the oxidation-reduction potentials. Aubel, Aubertin, and Genevois (1929) showed that anaerobic yeast cultures had an Eh of about 160 to 200 millivolts. In a study of the relation of metabolic processes to the oxidation-reduction potentials, Kluyver and Hoogerheide (1934) found that anaerobic fermentation began at an Eh of about 90 millivolts while aerobic fermentation began at a potential of about 160-250 millivolts. They found it possible to determine the dominant type of metabolism (i.e., respiration or fermentation) carried on in a yeast culture by observing the oxidation-reduction potential. In a recent report by Tang and Lin (1936) the results are given of an investigation on the effects of the unicellular algae Chlorella vulgaris and C. pyrenoidosa on the oxidation-reduction potentials and pH of a synthetic nutrient solution. As shown with bacteria and yeasts, these algae also lowered the Eh of the media when respiration was the dominant type of metabolism-i.e., when the potentials were measured in darkness. In the presence of light, when presumably photosynthesis was the dominant process, the El values became more positive.