Search results for "Pyruvate carboxylase"
showing 7 items of 27 documents
Activity and activation state of ribulose-1,5-bisphosphate carboxylase of spruce trees with varying degrees of damage relative to the occurrence of n…
1989
The aim was to determine whether a reduced carboxylation efficiency in needles of damaged spruce trees (Picea abies), is derived from a direct impairment of the ribulose-1,5-bisphosphate carboxylase (RuBP carboxylase) or there is an indirect inhibition of the RuBP carboxylase. In 1985, 1986 and 1987 measurements of RuBP carboxylase activity were carried out at three locations. Trees of different ages and degrees of damage were examined. RuBP carboxylase was assayed using both a rapid extraction method to determine the initial activity and an in vitro test after total activation to determine the total activity. The activation state was calculated as the ratio of initial activity to total act…
Investigations on the phosphoenolpyruvate carboxylase activity of spruce needles relative to the occurrence of novel forest decline
1991
Summary Investigations were carried out on phosphoenolpyruvate carboxylase (PEPC) activity in needles of Norway spruce trees [ Picea abies (L.) Karst.] at two natural sites during the course of three vegetation periods. PEPC activity found in needles of damaged trees was considerably higher than in needles of undamaged trees. Annual average figures varied up to 100%. The positive correlation between PEPC activity and the extent of damage of the investigated needles indicates a significant relationship between both parameters: the PEPC activity in spruce needles seems to be not only a qualitative, but also a quantitative indicator of the extent of damage. Higher PEPC activity in needles of d…
Formation of l(-)malate by Saccharomyces cerevisiae during fermentation
1988
When grown in a synthetic medium most of the 51 strains of the genera Saccharomyces, Saccharomycodes, Zygosaccharomyces and Schizosaccharomyces investigated formed l-malate during fermentation. The quantity varied between 0.1 and 2.6 g malate per liter. Two strains of Saccharomyces cerevisiae synthesized malate at a rate of about 1.5 g/l. Malate was liberated during the growth phase and not metabolized during the stationary phase. Optimum malate formation was observed at a sugar concentration of about 20% (w/v), at pH 5 and at suboptimal nitrogen concentrations of less than 300 mg N/liter. Of the amino acids aspartate and glutamate were most favourable. If ammonium salts were used as the ni…
Correlative Analysis of the Photosynthetic Capacity and Different Components of the Photosynthetic Apparatus
1984
The majority of higher plants is able to adapt to the ecological factor light in a wide range. Depending on the light intensity and the light quality during growth, plant with an equal genotype develop into so-called low light and high light forms. The photosynthetic adaptation to different light conditions involves complex, balanced changes of many leaf features. The changes of physiological factors of photosynthesis includes differences in the CO2 conductance, in the Calvin cycle enzymes, the capacity of electron transport, the photophosphorylation and the pigments (Boardman, 1977; Wild, 1979; Bjorkman, 1981; Lichtenthaler et al., 1981). The adaptation of individual plants or leaves to lo…
Reversible inhibition of CO2fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase through the synergic effect of arsenite and a monothiol
2013
The activity of the photosynthetic carbon-fixing enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), is partially inhibited by arsenite in the millimolar concentration range. However, micromolar arsenite can fully inhibit Rubisco in the presence of a potentiating monothiol such as cysteine, cysteamine, 2-mercaptoethanol or N-acetylcysteine, but not glutathione. Arsenite reacts specifically with the vicinal Cys172-Cys192 from the large subunit of Rubisco and with the monothiol to establish a ternary complex, which is suggested to be a trithioarsenical. The stability of the complex is strongly dependent on the nature of the monothiol. Enzyme activity is fully recovered through …
REDOX PROPERTIES ARE CONSERVED IN RUBISCOS FROM DIATOMS AND GREEN ALGAE THROUGH A DIFFERENT PATTERN OF CYSTEINES1
2010
Eukaryotic RUBISCO appears in two sequence-diverging forms, known as red-like (present in nongreen algae) and green-like (of green algae and higher plants) types. Oxidation of cysteines from green-like RUBISCOs is known to result in conformational changes that inactivate the enzyme and render a relaxed structure more prone to proteolytic attack. These changes may have regulatory value for green algae and higher plants, promoting RUBISCO catabolism under stress conditions. We compare here red-like RUBISCOs from several diatoms with a representative green-like RUBISCO from Chlamydomonas reinhardtii, paying special attention to the cysteine-dependent redox properties. Purified diatom RUBISCO p…
Aging of the liver: Age-associated mitochondrial damage in intact hepatocytes
1996
Mitochondrial damage may be a major cause of cellular aging. So far, this hypothesis had only been tested using isolated mitochondria. The aim of this study was to investigate the involvement of mitochondria in aging using whole liver cells and not isolated mitochondria only. Using flow cytometry, we found that age is associated with a decrease in mitochondrial membrane potential (30%), an increase in mitochondrial size, and an increase in mitochondrial peroxide generation (23%). Intracellular peroxide levels were also increased. The number of mitochondria per cell and inner mitochondrial membrane mass did not change. Gluconeogenesis from glycerol or fructose (mitochondrial-independent) did…