Influence of temperature and salinity on carbon and nitrogen content in Dunaliella viridis teodoresco under nitrogen sufficiency

Cell carbon and nitrogen in D. viridis are strongly dependent on the culturing conditions. Both elements increase with increasing salinity. At 31°C cell carbon is maximum and cell nitrogen minimum. This temperature was described previously (Jiménez, C., Niell, F. X. & Fernandez, J. A. (1990). Hydrobiologia, 197, 165-72) as the optimal one for achieving the maximum oxygen evolution. These results point out a possible competence for the reducing power during carbon and nitrogen assimilation processes, and under conditions of high photosynthesis (carbon assimilation) there is a partial inhibition of nitrate reduction, making C:N ratio maximum under conditions of maximum net photosynthesis.The study of cell glycerol, nitrate, structural proteins and free amino acids indicates that all of these solutes accumulate in the cells as a result of the high salinity adaptation.     

Highly efficient bioconversion of glucose into fructose diphosphate with fed-batch-grown Saccharomyces cerevisiae cells

Summary One of the methods commonly used for manufacturing fructose 1,6-diphosphate is based on the enzymatic phosphorylation of glucose with inorganic phosphate using permeabilized brewer's yeast cells. Our results demonstrate that a substantial improvement in the yield of bioconversion can be achieved using fed-batch-grown Saccharomyces cerevisiae cells. Under an appropriate glucose and phosphate to cell ratio the efficiency of bioconversion reaches 70% of the theoretical value. Offprint requests to: C. Compagno     

Oxidation-reduction potentials of the hemes in cytochrome C3 from Desulfovibrio gigas in the presence and absence of ferredoxin by EPR spectroscopy.

1. Ferricytochrome c3 from D. gigas exhibits two low-spin ferric heme EPR resonances with gz-values at 2.959 and 2.853. Ferrocytochrome c3 is diamagnetic based on the absence of any EPR signals. 2. EPR potentiometric titrations result in the resolution of the two low-spin ferric heme resonances into two additional heme components representing in total the four hemes of the cytochrome, with EM values of -235 mV and -315 mV at heme resonance I and EM values of -235 mV and -306 mV at heme resonance II. 3. EPR spectroscopy has detected a significant diminution of intensity (approx. 60 p. 100) in the gx amplitude of ferricytochrome c3 in the presence of D. gigas ferredoxin II. The presence of ferredoxin II also causes a more negative shift in the EM of the second components of the signals at heme resonances I and II of cytochrome C3. Both observations suggest that an interaction has occurred between cytochrome C3 and ferredoxin II. 4. The results presented suggest that the heme ligand environment of ferricytochrome c3 from D. gigas is less perturbed and/or less asymmetric than environment for ferricytochrome c3 from D. vulgaris whose EPR behavior indicates the non-equivalence of all four hemes.     

Purification,characterization and biological activity of three forms of ferredoxin from the sulfate-reducing bacterium Desulfovibrio gigas

Three forms of ferredoxin FdI, FdI′, and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI′ present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI′ and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI′ and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned.     

Responses of calves to a simulated altitude of 5000 m

Six calves were exposed in succession 12 days at 400 m altitude (control), 12 days at a simulated altitude of 5000 m in a low pressure chamber (experimental), and 14 days at 400 m altitude (recovery). Exposure to 5000 m produced the following changes: intake of feed and water decreased by 47 and 35% respectively, and body weight gain ceased. Rectal temperature rose by 0.4°C. Heart rate increased by 65%. Respiratory rate and blood pH increased moderately. There was an S-shaped rise of haematocrit (from 33 to 45%), which was paralleled by blood viscosity. Plasma viscosity showed a sharp, but transient rise. Short term measurements made during ascent to and descent from 5000 m altitude, both lasting for four hours, showed that some of the changes developed rapidly.     

Architecture and function of metallopeptidase catalytic domains

The cleavage of peptide bonds by metallopeptidases (MPs) is essential for life. These ubiquitous enzymes participate in all major physiological processes, and so their deregulation leads to diseases ranging from cancer and metastasis, inflammation, and microbial infection to neurological insults and cardiovascular disorders. MPs cleave their substrates without a covalent intermediate in a single‐step reaction involving a solvent molecule, a general base/acid, and a mono‐ or dinuclear catalytic metal site. Most monometallic MPs comprise a short metal‐binding motif (HEXXH), which includes two metal‐binding histidines and a general base/acid glutamate, and they are grouped into the zincin tribe of MPs. The latter divides mainly into the gluzincin and metzincin clans. Metzincins consist of globular ～130–270‐residue catalytic domains, which are usually preceded by N‐terminal pro‐segments, typically required for folding and latency maintenance. The catalytic domains are often followed by C‐terminal domains for substrate recognition and other protein–protein interactions, anchoring to membranes, oligomerization, and compartmentalization. Metzincin catalytic domains consist of a structurally conserved N‐terminal subdomain spanning a five‐stranded β‐sheet, a backing helix, and an active‐site helix. The latter contains most of the metal‐binding motif, which is here characteristically extended to HEXXHXXGXX(H,D). Downstream C‐terminal subdomains are generally shorter, differ more among metzincins, and mainly share a conserved loop—the Met‐turn—and a C‐terminal helix. The accumulated structural data from more than 300 deposited structures of the 12 currently characterized metzincin families reviewed here provide detailed knowledge of the molecular features of their catalytic domains, help in our understanding of their working mechanisms, and form the basis for the design of novel drugs.