The impact of spectral composition and light periodicity on the activity of two antioxidant enzymes (SOD and CAT) in the coral Favia favus

In oligotrophic waters the light spectrum is mostly blue, and therefore the physiological and biochemical responses to blue light occurring in the coral tissue and in the symbiotic algae are important. Examination of the wavelength dependence of two free radical scavenger enzyme activity revealed an increase in activity in the blue light range (440-480 nm) compared to the red (640680 nm) in the full visible light (400-700 nm) range. These data show for the first time the relationship between the action spectra of photosynthesis and the activity of two main antioxidant enzymes in the symbiotic coral Favia favus. It was found that in the animal (host) the enzyme response to the spectral distribution of light was higher than that of the zooxanthellae, probably due to accumulation of free radicals within the host tissue. Furthermore, we found that the activity of these enzymes is affected in nature by the length of the day and night, and in the laboratory, by the duration of the illumination. Changes in the pigment concentrations were also observed in response to growth under the blue region and the whole PAR spectrum, while fluorescence measurements with the fast repetition rate fluorometer (FRRF) showed a decrease in the sigma cross section and a decrease in the quantum yield also in the blue part of the spectrum. These changes of scavenger enzymes activity, pigment concentration and fluorescence yield at different light spectra are vital in acclimatization and survival of corals in shallow water environments with high light radiation. (c) 2005 Elsevier B.V. All rights reserved.

A novel suite of cyclotides from Viola odorata: sequence variation and the implications for structure, function and stability

Cyclotides are a fascinating family of plant-derived peptides characterized by their head-to-tail cyclized backbone and knotted arrangement of three disulfide bonds. This conserved structural architecture, termed the CCK (cyclic cystine knot), is responsible for their exceptional resistance to thermal, chemical and enzymatic degradation. Cyclotides have a variety of biological activities, but their insecticidal activities suggest that their primary function is in plant defence. In the present study, we determined the cyclotide content of the sweet violet Viola odorata, a member of the Violaceae family. We identified 30 cyclotides from the aerial parts and roots of this plant, 13 of which are novel sequences. The new sequences provide information about the natural diversity of cyclotides and the role of particular residues in defining structure and function. As many of the biological activities of cyclotides appear to be associated with membrane interactions, we used haemolytic activity as a marker of bioactivity for a selection of the new cyclotides. The new cyclotides were tested for their ability to resist proteolysis by a range of enzymes and, in common with other cyclotides, were completely resistant to trypsin, pepsin and thermolysin. The results show that while biological activity varies with the sequence, the proteolytic stability of the framework does not, and appears to be an inherent feature of the cyclotide framework. The structure of one of the new cyclotides, cycloviolacin O14, was determined and shown to contain the CCK motif. This study confirms that cyclotides may be regarded as a natural combinatorial template that displays a variety of peptide epitopes most likely targeted to a range of plant pests and pathogens.

Effects of anitoxidant supplementation and exercise training on erythrocyte antioxidant enzymes

Erythrocytes transport oxygen to tissues and exercise-induced oxidative stress increases erythrocyte damage and turnover. Increased use of antioxidant supplements may alter protective erythrocyte antioxidant mechanisms during training. Aim of study: To examine the effects of antioxidant supplementation, (alpha-lipoic acid and a-tocopherol) and/or endurance training on the antioxidant defenses of erythrocytes. Methods: Young male Wistar rats were. assigned to (1) sedentary; (2) sedentary and antioxidant-supplemented; (3) endurance-trained; or (4) endurance-trained and antioxidant-supplemented groups for 14 weeks. Erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activities, and plasma malondialdehyde (MDA) were then measured. Results: Antioxidant supplementation had no significant effect (p > 0.05) on activities of antioxidant enzymes in sedentary animals. Similarly, endurance training alone also bad no effect (p > 0.05). GPX (125.9 2.8 vs. 121.5 3.0 U.gHb(-1), p < 0.05) and CAT (6.1 0.2 vs. 5.6 0.2 U.mgHb-1, p < 0.05) activities were increased in supplemented trained animals compared to non-supplemented sedentary animals whereas SOD (61.8 4.3 vs. 52.0 5.2 U.mgHb(-1), p < 0.05) activity was decreased. Plasma MDA was not different among groups (p > 0.05). Conclusions: In a rat model, the combination of exercise training and antioxidant supplementation increased antioxidant enzyme activities (GPX, CAT) compared with each individual intervention.

Dimethylsulfide dehydrogenase from rhodovulum sulfidophilum: EPR spectroscopy and biochemical analysis reveal its place in the DMSO reductase family of molybdenum enzymes

Dimethylsulfide (DMS) dehydrogenase catalyses the oxidation of DMS to dimethylsulfoxide. The purified enzyme has three subunits of Mr = 94, 38 and 32 kDa and has an optical spectrum dominated by a b-type cytochrome. The metal ion and nucleotide analysis revealed 0.5 g-atom Mo, 9.8 g-atom Fe and 1.96 mol GMP per tool of enzyme. Taken together, these data indicate that DMS dehydrogenase contains a bis(MGD)Mo cofactor. A comparison of the Nterminal amino acid sequence of DMS dehydrogenase revealed that the Mo-containing ct-subunit was most closely related to the c~-subunits of nitrate reductase (NarG) and selenate reductase (SerA). Similarly, the [~-subunit of DMS dehydrogenase was most closely related to the [3-subunits of nitrate reductase (NarH) and selenate reductase (SerB). Variable temperature X-band EPR spectra (120-2K) of 'as isolated' DMS dehydrogenase showed resonances arising from multiple redox centres, Mo(V), [3Fe-4S] +, [4Fe-4S] ÷. A pH dependent EPR study of the Mo(V) centre in lH20 and 2H20 reveals the presence of three Mo(V) species in equilibrium, Mo(V)-OH2, Mo(V)-X and Mo(V)-OH. Between pH6 and 8.2 the dominant species is Mo(V)-OH2 and Mo(V)-X is a minor component. X is probably the anion, chloride. Comparison of the rhombicity and anisotropy parameters for the Mo(V) species in DMS dehydrogenase with other Mo(V) centres in metalloproteins showed that it was most similar to the low pH nitrite spectrum of E. coli nitrate reductase (NarGHI). The spin Hamiltonian parameters (2.0158, 1.8870, 1.8620) for the [4Fe-4S] + cluster suggests the presence of histidine (N) coordination to iron in this cluster. It is suggested that this unusual [Fe-S] cluster may be associated with a histidine-cysteine rich sequence at the N-terminus of the ct-subunit of DMS dehydrogenase.