Mode of action of bolesatine, a cytotoxic glycoprotein from Boletus satanas Lenz. Mechanistic approaches.

International audienceBolesatine is a potent cytotoxic glycoprotein purified from Boletus satanas Lenz, which has previously been shown to be an inhibitor of protein synthesis in several in vitro systems and in vivo. For a better understanding of its mechanism of action on protein synthesis at the ribosomal level, rat liver ribosomes were pretreated with bolesatine (1 to 10 micrograms) added to in vitro polyuridylic acid (poly(U)) translation systems before and after washing. The fact that ribosomes were still active confirmed that bolesatine cannot be included in the group of protein synthesis inhibitors of plant origin, known as ribosome-inactivating proteins (RIPs). The effect of bolesatine on the EF-2 elongation factor and post-ribosomal fraction was then studied in vitro. The results indicated that bolesatine does not have a direct effect on elongation factors, but hydrolyses the nucleoside triphosphates, GTP (80% to 90%, respectively for 1 to 10 micrograms) and ATP (10% to 40%, respectively for 1 to 10 micrograms), with consequent inhibition of protein synthesis. Thus, bolesatine should be classified as a nucleoside triphosphate phosphatase, rather than as a direct inhibitor of protein synthesis. The study of the effect of bolesatine on the EF-2 factor revealed that the mechanism whereby bolesatine affects protein synthesis probably involves GTP hydrolysis rather than EF-2 inhibition.Bolesatine is a potent cytotoxic glycoprotein purified from Boletus satanas Lenz, which has previously been shown to be an inhibitor of protein synthesis in several in vitro systems and in vivo. For a better understanding of its mechanism of action on protein synthesis at the ribosomal level, rat liver ribosomes were pretreated with bolesatine (1 to 10 micrograms) added to in vitro polyuridylic acid (poly(U)) translation systems before and after washing. The fact that ribosomes were still active confirmed that bolesatine cannot be included in the group of protein synthesis inhibitors of plant origin, known as ribosome-inactivating proteins (RIPs). The effect of bolesatine on the EF-2 elongation factor and post-ribosomal fraction was then studied in vitro. The results indicated that bolesatine does not have a direct effect on elongation factors, but hydrolyses the nucleoside triphosphates, GTP (80% to 90%, respectively for 1 to 10 micrograms) and ATP (10% to 40%, respectively for 1 to 10 micrograms), with consequent inhibition of protein synthesis. Thus, bolesatine should be classified as a nucleoside triphosphate phosphatase, rather than as a direct inhibitor of protein synthesis. The study of the effect of bolesatine on the EF-2 factor revealed that the mechanism whereby bolesatine affects protein synthesis probably involves GTP hydrolysis rather than EF-2 inhibition

Bioactive compounds in seaweed; functional food applications and legislation

Seaweed is more than the wrap that keeps rice together in sushi. Seaweed biomass is already used for a wide range of other products in food, including stabilising agents. Biorefineries with seaweed as feedstock are attracting worldwide interest and include low-volume, high value-added products and vice versa. Scientific research on bioactive compounds in seaweed usually takes place on just a few species and compounds. This paper reviews worldwide research on bioactive compounds, mainly of nine genera or species of seaweed, which are also available in European temperate Atlantic waters, i.e. Laminaria sp., Fucus sp., Ascophyllum nodosum, Chondrus crispus, Porphyra sp., Ulva sp., Sargassum sp., Gracilaria sp. and Palmaria palmata. In addition, Undaria pinnatifida is included in this review as this is globally one of the most commonly produced, investigated and available species. Fewer examples of other species abundant worldwide have also been included. This review will supply fundamental information for biorefineries in Atlantic Europe using seaweed as feedstock. Preliminary selection of one or several candidate seaweed species will be possible based on the summary tables and previous research described in this review. This applies either to the choice of high value-added bioactive products to be exploited in an available species or to the choice of seaweed species when a bioactive compound is desired. Data are presented in tables with species, effect and test organism (if present) with examples of uses to enhance comparisons. In addition, scientific experiments performed on seaweed used as animal feed are presented, and EU, US and Japanese legislation on functional foods is reviewed