Beneficial and harmful roles of bacteria from the Clostridium genus

Bacteria of the Clostridium genus are often described only as a biological threat and a foe of mankind. However, many of them have positive properties and thanks to them they may be used in many industry branches (e.g., in solvents and alcohol production, in medicine, and also in esthetic cosmetology). During the last 10 years interest in application of C. botulinum and C. tetani in medicine significantly increased. Currently, the structure and biochemical properties of neurotoxins produced by these bacterial species, as well as possibilities of application of such toxins as botulinum as a therapeutic factor in humans, are being intensely researched. The main aim of this article is to demonstrate that bacteria from Clostridium spp. are not only pathogens and the enemy of humanity but they also have many important beneficial properties which make them usable among many chemical, medical, and cosmetic applications

Biochemical characterization of L-asparaginase isoforms from Rhizobium etli—the boosting effect of zinc

L-Asparaginases, divided into three structural Classes, catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia. The members of Class 3, ReAIV and ReAV, encoded in the genome of the nitrogen fixing Rhizobium etli, have the same fold, active site, and quaternary structure, despite low sequence identity. In the present work we examined the biochemical consequences of this difference. ReAIV is almost twice as efficient as ReAV in asparagine hydrolysis at 37°C, with the kinetic KM, kcat parameters (measured in optimal buffering agent) of 1.5 mM, 770 s-1 and 2.1 mM, 603 s-1, respectively. The activity of ReAIV has a temperature optimum at 45°C–55°C, whereas the activity of ReAV, after reaching its optimum at 37°C, decreases dramatically at 45°C. The activity of both isoforms is boosted by 32 or 56%, by low and optimal concentration of zinc, which is bound three times more strongly by ReAIV then by ReAV, as reflected by the KD values of 1.2 and 3.3 μM, respectively. We also demonstrate that perturbation of zinc binding by Lys→Ala point mutagenesis drastically decreases the enzyme activity but also changes the mode of response to zinc. We also examined the impact of different divalent cations on the activity, kinetics, and stability of both isoforms. It appeared that Ni2+, Cu2+, Hg2+, and Cd2+ have the potential to inhibit both isoforms in the following order (from the strongest to weakest inhibitors) Hg2+ > Cu2+ > Cd2+ > Ni2+. ReAIV is more sensitive to Cu2+ and Cd2+, while ReAV is more sensitive to Hg2+ and Ni2+, as revealed by IC50 values, melting scans, and influence on substrate specificity. Low concentration of Cd2+ improves substrate specificity of both isoforms, suggesting its role in substrate recognition. The same observation was made for Hg2+ in the case of ReAIV. The activity of the ReAV isoform is less sensitive to Cl− anions, as reflected by the IC50 value for NaCl, which is eightfold higher for ReAV relative to ReAIV. The uncovered complementary properties of the two isoforms help us better understand the inducibility of the ReAV enzyme

DataSheet1_Biochemical characterization of L-asparaginase isoforms from Rhizobium etli—the boosting effect of zinc.pdf

L-Asparaginases, divided into three structural Classes, catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia. The members of Class 3, ReAIV and ReAV, encoded in the genome of the nitrogen fixing Rhizobium etli, have the same fold, active site, and quaternary structure, despite low sequence identity. In the present work we examined the biochemical consequences of this difference. ReAIV is almost twice as efficient as ReAV in asparagine hydrolysis at 37°C, with the kinetic KM, kcat parameters (measured in optimal buffering agent) of 1.5 mM, 770 s-1 and 2.1 mM, 603 s-1, respectively. The activity of ReAIV has a temperature optimum at 45°C–55°C, whereas the activity of ReAV, after reaching its optimum at 37°C, decreases dramatically at 45°C. The activity of both isoforms is boosted by 32 or 56%, by low and optimal concentration of zinc, which is bound three times more strongly by ReAIV then by ReAV, as reflected by the KD values of 1.2 and 3.3 μM, respectively. We also demonstrate that perturbation of zinc binding by Lys→Ala point mutagenesis drastically decreases the enzyme activity but also changes the mode of response to zinc. We also examined the impact of different divalent cations on the activity, kinetics, and stability of both isoforms. It appeared that Ni2+, Cu2+, Hg2+, and Cd2+ have the potential to inhibit both isoforms in the following order (from the strongest to weakest inhibitors) Hg2+ > Cu2+ > Cd2+ > Ni2+. ReAIV is more sensitive to Cu2+ and Cd2+, while ReAV is more sensitive to Hg2+ and Ni2+, as revealed by IC50 values, melting scans, and influence on substrate specificity. Low concentration of Cd2+ improves substrate specificity of both isoforms, suggesting its role in substrate recognition. The same observation was made for Hg2+ in the case of ReAIV. The activity of the ReAV isoform is less sensitive to Cl− anions, as reflected by the IC50 value for NaCl, which is eightfold higher for ReAV relative to ReAIV. The uncovered complementary properties of the two isoforms help us better understand the inducibility of the ReAV enzyme.</p