Purification and characterization of a psychrophilic glutathione reductase from Antarctic ice microalgae Chlamydomonas sp. strain ICE-L. Polar Biol

Polar Biology (Impact Factor: 1.59). 11/2007; 31(1):23-30. DOI: 10.1007/s00300-007-0328-5


A psychrophilic glutathione reductase from Antarctic ice microalgae Chlamydomonas sp. Strain ICE-L was purified by ammonium sulfate fractionation and three steps of chromatography. The yield was up to 25.1%
of total glutathione reductase in the crude enzyme extract. The glutathione reductase activity was characterized by the spectrophotometric
method under different conditions. Purified glutathione reductase was separated by SDS-PAGE, which furnished a homogeneous
band. The native molecular mass of the enzyme was 115 kDa. Apparent Km values for NADPH and NADH (both at 0.5 mmol L−1 oxidized glutathione) were 22.3 and 83.8 μmol L−1, respectively. It was optimally active at pH 7.5, and it was stable from pH 5 to 9. Its optimum temperature was 25�C, with
activity at 0�C 23.5% of the maximum. Its optimum ion strength and optimum Mg2+ were 50–90 and 7.5 mmol L−1, respectively. Ca2+, Mg2+, and cysteine substantially increased the activity of the enzyme but chelating agents, heavy metals (Cd2+, Pb2+, Cu2+, Zn2+, etc.), NADPH, and ADP had significant inhibitory effects. This glutathione reductase can be used to study the adaptation
and mechanism of catalysis of psychrophilic enzymes, and it has a high potential as an environmental biochemical indicator
under extreme conditions.

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    • "Last, glutathione reductase purified from Chlamydomonas sp. ICE-L exhibits an increasing catalytic rate at temperatures ranging from 0 to 25 °C, as well as enhanced thermolability (Ding et al. 2007). Further characterization of cold-adapted enzymes and the comparison to their thermostable homologs will help to elucidate which structural modifications are important for catalytic activity at low temperature. "
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    ABSTRACT: Permanently cold habitats dominate our planet and psychrophilic microorganisms thrive in cold environments. Environmental adaptations unique to psychrophilic microorganisms have been thoroughly described; however, the vast majority of studies to date have focused on cold-adapted bacteria. The combination of low temperatures in the presence of light is one of the most damaging environmental stresses for a photosynthetic organism: in order to survive, photopsychrophiles (i.e. photosynthetic organisms adapted to low temperatures) balance temperature-independent reactions of light energy capture/transduction with downstream temperature-dependent metabolic processes such as carbon fixation. Here, we review research on photopsychrophiles with a focus on an emerging model organism, Chlamydomonas raudensis UWO241 (UWO241). UWO241 is a psychrophilic green algal species and is a member of the photosynthetic microbial eukaryote community that provides the majority of fixed carbon for ice-covered lake ecosystems located in the McMurdo Dry Valleys, Antarctica. The water column exerts a range of environmental stressors on the phytoplankton community that inhabits this aquatic ecosystem, including low temperatures, extreme shade of an unusual spectral range (blue-green), high salinity, nutrient deprivation and extremes in seasonal photoperiod. More than two decades of work on UWO241 have produced one of our most comprehensive views of environmental adaptation in a cold-adapted, photosynthetic microbial eukaryote.
    Extremophiles 08/2013; 17(5). DOI:10.1007/s00792-013-0571-3 · 2.31 Impact Factor
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    ABSTRACT: Stichococcus, a genus of green algae, distributes in ice-free areas throughout Antarctica. To understand adaptive strategies of Stichococcus to permanently cold environments, the physiological responses to temperature of two psychrotolerants, S. bacillaris NJ-10 and S. minutus NJ-17, isolated from rock surfaces in Antarctica were compared with that of one temperate S. bacillaris FACHB753. Two Antarctic Stichococcus strains grew at temperature from 4 to 25°C, while the temperate strain could grow above 30°C but could not survive at 4°C. The photosynthetic activity of FACHB753 at lower than 10°C was less than that of Antarctic algae. Nitrate reductase in NJ-10 and NJ-17 had its optimal temperature at 20°C, in comparison, the maximal activity of nitrate reductase in FACHB753 was found at 25°C. When cultured at 4-15°C a large portion of unsaturated fatty acids in the two Antarctic species was detected and the regulation of the degree of unsaturation of fatty acids by temperature was observed only above 15°C, though the content of the major unsaturated fatty acid αC18:3 in FACHB753 decreased with the temperatures elevated from 10 to 25°C. Elevated nitrate reductase activity and photosynthetic rates at low temperatures together with the high proportion of unsaturated fatty acids contribute to the ability of the Antarctic Stichococcus to thrive.
    Extremophiles 11/2011; 16(1):127-33. DOI:10.1007/s00792-011-0412-1 · 2.31 Impact Factor
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    ABSTRACT: A cDNA (GenBank ID: GU395492) encoding cytosolic glutathione reductase (named ICE-LGR) in Antarctic microalgae Chlamydomonas sp. ICE-L was successfully cloned by RT-PCR and rapid amplification of cDNA ends technique (RACE). The expression patterns of ICE-LGR under different salinity stresses were determined by real-time PCR. ICE-LGR cDNA has 1913 bp nucleotides with an open reading frame (ORF) of 1458 bp, encoding 485 amino acid residues. The deduced amino acid sequence shows 79% homology with glutathione reductase (GR) of Chlamydomonas reinhardtii. Activity assessment and mRNA expression analysis results showed that activity and expression level of GR in ICE-L cells were up-regulated under either high or low salinity. Together, our results revealed that ICE-LGR might play an important role in Antarctic ice algae Chlamydomonas sp. ICE-L acclimatizing to polar high salinity environment as well as low salinity. These results provide us valuable information on further investigating the molecular mechanism of ICE-LGR.
    Marine Genomics 03/2012; 5:59-64. DOI:10.1016/j.margen.2011.11.001 · 1.79 Impact Factor
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