title: Iodometric method for detection of beta-lactamase activity in yeast cells carrying ampicillin resistance gene in chimeric plasmids.
abstract: In order to determine whether an ampicillin resistance gene in a chimeric plasmid is active in transformed yeast cells, it is necessary to have a simple and quick assay procedure. We describe here a procedure for achieving this goal using an iodometric color reaction. This method is based on the fact that the ampicillin resistance gene product, beta-lactamase, can hydrolyze penicillin G and release a reducing product, which can be visualized by the discoloration of a dark blue iodine-starch complex. We have improved this method so that the assay can be carried out on agar plate and in liquid culture. It permits the detection of the beta-lactamase enzyme activity in yeast liquid culture at a concentration as low as 1 X 10(5) cells/ml within 12 h. This method is especially useful for certain yeast transformation systems, such as industrial yeast cultures, where the transformants can be selected only by drug resistance.
authors.affiliation: Institute of Botany, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: S S
authors.initials: SS
authors.lastname: Kuo
authors.forename: T Y
authors.initials: TY
authors.lastname: Feng
mesh_terms: D000668:Ampicillin Resistance / Q000235:genetics*; D003124:Colorimetry; D007455:Iodine; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D013213:Starch; D014170:Transformation, Genetic; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D013213:Starch; D007455:Iodine; D001618:beta-Lactamases