Quantitative Assay of Endotoxin by the Use of Ammonia Electrode and Purified Factor C

Abstract

Factor C, an endotoxin-sensitive serine-protease zymogen, was prepared by cation-exchange chromatography using SP Toyopearl 650C. This preparation exhibited a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The endotoxine-dependent Factor C activity was determined from the amount of released ammonium ions by cleavage of N-tert-butoxy-carbonl Val-Pro-Arg-NH₂ using an ammonia electrode. The sensitivity towards the endotoxin was approximately 5×10^-8 g/ml.