Enzymatic properties of cloacin DF13 and kinetics of ribosome inactivation.
1. The cloacin DF13-induced inactivation of ribosomes in vitro can be described as an enzyme-catalyzed reaction according to the Michaelis-Menten equation. Most probably the cloacin acts as a unique endoribonuclease. 2. At pH 7.8 and 37 degrees C the Km value for the reaction of cloacin DF13 with ribosomes is 13.2 - 10(-6) M. If under these conditions the reaction mixture is supplemented with all components necessary for protein synthesis, the Km changes to 17.7 - 10(-6) M. 3. The in vitro activity of cloacin DF13 has a temperature optimum of 43 degrees C at pH 7.8 and a pH optimum of 8.4 at 37 degtees C. 4. Experiments with cloacin DF13-immunity protein as an inhibitor of the cloacin activity in vitro have indicated that the immunity protein might be considered as a non-competitive and virtually "irreversible" inhibitor.
D004755:Enterobacteriaceae / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D014176:Protein Biosynthesis / Q000187:drug effects; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D014118:Toxins, Biological / Q000378:metabolism* / Q000494:pharmacology
D014118:Toxins, Biological