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K Sigler

Publications and source records attributed to K Sigler.

78 records · Page 5Linked to original sources
PubMed1978

Effect of inhibitors on acid production by baker's yeast.

Glucose-induced acid extrusion, respiration and anaerobic fermentation in baker's yeast was studied with the aid of sixteen inhibitors. Uranyl(2+) nitrate affected the acid extrusion more anaerobically than aerobically; the complexing of Mg2+ and Ca2+ by EDTA at the membrane had no effect. Inhibitors of glycolysis (iodoacetamide, N-ethylmaleimide, fluoride) suppressed acid production markedly, and so did the phosphorylation-blocking arsenate. Fluoroacetate, inhibiting the citric-acid cycle, had no effect. Inhibition by uncouplers depended on their pKa values: 2,4,6-trinitrophenol (pKa 0.4) less than 2,4-dinitrophenol (4.1) less than azide (4.7) less than 3-chlorophenylhydrazonomalononitrile (6.0). Inhibition by trinitrophenol was only slightly increased by its acetylation. Cyanide and nonpermeant oligomycin showed practically no effect; inhibition by dicyclohexylcarbodiimide was delayed but potent. The concentration profiles of inhibition of acid production differed from those of respiration and fermentation. Thus, though the acid production is a metabolically dependent process, it does not reflect the intensity of metabolism, except partly in the first half of glycolysis.

Acids↗
PubMed1976

Some properties of the adenosine triphosphatase systems of two yeast species, Saccharomyces cerevisiae and Rhodotorula glutinis.

1. Total ATPase levels were determined in homogenate fractions of baker's yeast, Saccharomyces cerevisiae K and Rhodotorula glutinis. The maximum ATPase activities in 8000 X g supernatant of the three yeast strains were 6.0, 1.9, and 2.2 mmol Pih-1 (gDS)-1, respectively; the activities in the sediment were somewhat higher. Exponential cells of S. cerevisiae K and R. glutinis exhibited higher ATPase levels than did the stationary cells. 2. The total ATPase activity in both yeast species showed a maximum at ph 6.8 a minimum at pH 7.2, and another broader masimum around pH 8.0. 3. No significant NaK-ATPase activity was detected in baker's yeast, in either the exponential or the stationary cells of R. glutinis, and in exponential S. cerevisiae K cells in the pH range of 6.0-9.3. 4. Stationary cells of S. cerevisiae K exhibited, at pH 7.0-8.5, A Na,K-ATPase activity attaining 9% of total ATPase level. 5.3 X 10(-3) M phenylmethyl sulphonyl fluoride had no effect on the total ATPase level in S. cerevisiae and inhibited the activity in R. glutinis by 25%; it did not bring forth any Na,K-ATPase activity apart from that found in its absence. 6. 1.5 M urea lowered the ATPase activity in R. glutinis by 68% but had no effect on S. cerevisiae cells. 10(-5) M dicyclohexylcarbodiimide suppressed the ATPase activity in S. cerevisiae and R. glutinis by 74 and 79%, respectively. Neither agent revealed and additional Na,K-ATPase activity. 7. The comparison of Na,K-ATPase activities with data on K+ fluxes across the yeast plasma membrane suggested that even with the lower flux values the Na,K-ATPase, even if present, would account for a mere 40% of transported ions. The results imply that the active ion transport in yeasts is energized by mechanisms other than the Na,K-ATPase.

Adenosine Triphosphatases↗
PubMedDate not supplied

Suppression of radical-induced lipid peroxidation in a model system by alkyl esters of cinnamate quaternary ammonium salts.

Three new groups of phenolic antioxidants, quaternary ammonium salts with a phenol ring and alkyl chains of different length (pyrrolidine ethyl esters of 3,5-di-t-butyl-4-hydroxydihydrocinnamic acid n-alkoxymethylchlorides (PYE-n) or n-alkylbromides (PYA-n) and 2-dimethylaminoethyl ester n-alkylbromides (PPA-n), were synthesized. Some of them were previously found to efficiently protect yeast cells against oxidants and to inhibit the production of thiobarbituric acid-reactive substances in whole yeast cells and in isolated membrane lipids. The new antioxidants (at 1-100 microM) abolished or diminished peroxidation of olive oil emulsions caused by the OH*-producing Fe2+ and RO* and ROO*-producing tert-butylhydroperoxide (TBHP) and the azo compounds 2,2'-azobis-(amidinopropane)dihydronitrile (AAPH) and 1,1'-azobis-(1-cyclohexanecarbonitrile) (ACHN): all present at 10 mM. The efficiency of individual both antioxidants was examined in relation to the type of lipid peroxidation inducer, the site of antioxidant incorporation into the emulsion lipid phase, the length of the alkyl chain, and the maximum concentration of effective antioxidant monomers given by its critical micelle concentration. PYA-n class compounds were highly efficient against all peroxidation inducers and their efficiency did not depend on the position of their molecules in the lipid phase and/or on the aliphatic chain length. In contrast, the efficiency of PYE-n and PPA-n class compounds depended both on the type of oxidant and on the length of their aliphatic chain. Their potency against Fe2+ and ACHN increased with increasing alkyl chain length whereas with AAPH it dropped with increasing alkyl chain length. A similar pattern was found with the action of PYE-n against TBHP whereas in the PPA-n group an extending alkyl chain reduced the anti-TBHP efficiency. These relationships may not be entirely straightforward and other factors (chemical nature of each compound, its possible interaction with fluorescent probes used for diagnostics, etc.) may play a considerable and not yet quite clear role. PPA-n class antioxidants have the lowest critical micelle concentration, which may limit their efficiency. Nevertheless, these phenolic antioxidants can be conveniently employed as highly efficient inhibitors of lipid peroxidation.

Antioxidants↗