[Production and purification of thermolabile enterotoxin of Escherichia coli (author's transl)].

: Heat labile enterotoxin (LT toxin) of Escherichia coli could be produced optimally and quantitatively in a trypticase soy broth with 0.2% yeast extract after 12 hours. Treatment of the cells with polymyxin B increased the yield of LT toxin. After concentration by ammonium sulphate precipitation, the LT toxin fraction was separated successfully from other proteins by Ultrogel AcA-34 gel exclusion chromatography. A 0.15 mol/l Tris-HCl buffer with gradually increasing pH was used as eluent. Purity was determined by gel electrophoresis. The presence of LT toxin in one isolated fraction ws demonstrated in vitro by assaying activity in the intestines of rats (by collection of liquid and quantification of cAMP in intestinal fluid). The reproducibility of the LT fraction was ascertained by a specific radioimmunoassay (RIA) and by an enzyme-linked immunosorbent assay (ELISA). The LT fraction had a molecular weight of 72,000 dalton. Two subunits of the toxin with molecular weights of 30,000 and 40,000 dalton respectively were found.