Kinetics of photoinactivation and photooxidation of mitomycin C in the presence of riboflavin.
The kinetic relation between the photoinactivation and photooxidation of mitomycin C in the presence of riboflavin was investigated. The photoinactivation was tested for lambda-phage induction in Escherichia coli K-12 (lambda) cells and colony formation of E. coli Bs-1 cells. Mitomycin C lost its phage-inducing and antibiotic activities when the antibiotic was irradiated in vitro with visible light in the presence of riboflavin. The loss of phage-inducing activity followed a Stern-Volmer type equation with respect to the dose of irradiation, and the inactivation constant was evaluated to be 0.96X10(-4)m2/J. The initial rate of decay of mitomycin C by photooxidation in the presence of riboflavin obeyed first order kinetics, and its cross section was estimated to be 2.51X10(-6)m/J independent of the intensity of incident light. The cross section for photooxidation was found to be proportional to the inactivation constant. These results suggest that the photoinactivation of mitomycin C is caused by its photooxidation. In order to rationalize this conclusion, a mechanism of photooxidation was proposed and reactions in vivo of the photoproduct were discussed in relation to the inactivation.
D010582:Bacteriophage lambda / Q000187:drug effects; D004926:Escherichia coli / Q000254:growth & development; D007700:Kinetics; D008027:Light; D008937:Mitomycins / Q000494:pharmacology / Q000528:radiation effects*; D010084:Oxidation-Reduction; D012256:Riboflavin; D014775:Virus Activation / Q000187:drug effects
D008937:Mitomycins; D012256:Riboflavin