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Archives of Biochemistry and Biophysics 07/1980; 202(1):187-200. · 2.93 Impact Factor
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Archives of Biochemistry and Biophysics 07/1980; 202(1):172-86. · 2.93 Impact Factor
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ABSTRACT: The levels of various enzymes and components of the glycolytic and respiratory pathways of the yeast Saccharomyces cerevisiae have been determined during a step-down, anaerobic-to-aerobic transition. These activities were determined as an adjunct to the respective metabolite data reported in the first paper in this series. It is clear from the data that anaerobic conditions induce an environment conducive to express glycolytic enzyme activities, while manifesting a differential induction/repression effect on oxidative enzymes. An NAD/NADH mediated mechanism is proposed to explain this difference. Of the enzymes assayed only cytochrome c oxidase shows any direct response to oxygen challenge and consequently it is suggested that the assembly of this enzyme is the trigger mechanism and rate-limiting step in aerobic adaptation.
Canadian Journal of Microbiology 07/1975; 21(6):855-61. · 1.36 Impact Factor
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ABSTRACT: As a corollary to the metabolite data obtained from yeast cultures undergoing an exponential anaerobic-aerobic phase transition, levels of various glycolytic and citric acid cycle enzyme activities have been monitored in these cells. The relation of the changes in these enzyme activities in cells grown on either glucose or galactose is discussed on light of different metabolic postures these cells demonstrate as a result of their transitions. A general discussion is presented which compares the results obtained in this series of papers from both step-down and exponential transfer experiments and relates these data to control of mitochondriogenesis in yeast.
Canadian Journal of Microbiology 07/1975; 21(6):869-76. · 1.36 Impact Factor
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ABSTRACT: The changes in mechanism of control and in the mode of metabolism which yeast cells undergo when an anaerobic-aerobic transition is imposed on them has received much attention. One experimental approach to this type of investigation has been a step-down transition. The data from our experiments (cf. papers I and II of this series) has shown that this model is too complex to arrive at meaningful interpretation. We therefore repeated these measurements of glycolytic and citric acid cycle metabolites in cells growing on either glucose or galactose media and exposed to exponential N2 yields 02 transitions. This type of experiment is designed to examine directly the effect of oxygen challenge. Interpretation of this new data shows that the major metabolic control operating in the two hexose cultures are different and suggests that adenine nucleotide controls glucose cells whereas galactose cell metabolism is controlled by the NAD/NADH balance. This concept is discussed.
Canadian Journal of Microbiology 07/1975; 21(6):862-8. · 1.36 Impact Factor
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ABSTRACT: Membrane lipids of yeast mitochondria have been enriched by growing yeast cells in minimal medium supplemented with specific unsaturated fatty acids as the sole lipid supplement. Using the activity of marker enzymes for the outer (kynurenine hydroxylase) and inner (cytochrome c oxidase and oligomycin-sensitive ATPase) mitochondrial membranes, Arrhenius plots have been constructed using both promitochondria and mitochondria obtained from O2-adapting cells in the presence of a second unsaturated fatty acid (i.e. linoleate (N2) to elaidic (O2)). Transition temperatures which reflect the unsaturated fatty acid enrichment of the new membranes reveal interesting features involved in the mechanism of the assembly of these two mitochondrial membranes. This approach was further enforced with both lipid depletion and mitochondrial protein inhibition studies. Kynurenine hydroxylase which does not require fatty acid for its continued synthesis during aerobiosis seems to be incorporated into the preformed linoleate-anaerobic outer membrane. The newly synthesized activities of inner mitochondrial membrane enzymes on the other hand, appear to integrate their activity into newly formed aerobic-elaidic-rich inner membrane. These latter enzymes show a distinct dependence on fatty acid supplement for their continued synthesis during their aerobic phase. This suggests that O2-dependent proteo-lipid precursors are formed before these enzymes are integrated into their membrane mosaic. Two separate models are proposed to explain these results, one for the lipid-rich outer mitochondrial membrane and another for the protein-rich inner mitochondrial membrane.
Biochimica et Biophysica Acta 03/1975; 375(3):446-61. · 4.66 Impact Factor
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Biochemical and Biophysical Research Communications 07/1972; 47(6):1299-305. · 2.48 Impact Factor
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Canadian Journal of Microbiology 09/1971; 17(8):1125-31. · 1.36 Impact Factor
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Biochemical Journal 03/1970; 116(4):23P-24P. · 4.90 Impact Factor
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Biochimica et Biophysica Acta 03/1970; 199(2):476-89. · 4.66 Impact Factor
