title: Rapid method using two microbial enzymes for detection of L-abrine in food as a marker for the toxic protein abrin.
abstract: Abrin is a toxic protein produced by the ornamental plant Abrus precatorius, and it is of concern as a biothreat agent. The small coextracting molecule N-methyl-l-tryptophan (l-abrine) is specific to members of the genus Abrus and thus can be used as a marker for the presence or ingestion of abrin. Current methods for the detection of abrin or l-abrine in foods and other matrices require complex sample preparation and expensive instrumentation. To develop a fast and portable method for the detection of l-abrine in beverages and foods, the Escherichia coli proteins N-methyltryptophan oxidase (MTOX) and tryptophanase were expressed and purified. The two enzymes jointly degraded l-abrine to products that included ammonia and indole, and colorimetric assays for the detection of those analytes in beverage and food samples were evaluated. An indole assay using a modified version of Ehrlich's/Kovac's reagent was more sensitive and less subject to negative interferences from components in the samples than the Berthelot ammonia assay. The two enzymes were added into food and beverage samples spiked with l-abrine, and indole was detected as a degradation product, with the visual lower detection limit being 2.5 to 10.0 μM (∼0.6 to 2.2 ppm) l-abrine in the samples tested. Results could be obtained in as little as 15 min. Sample preparation was limited to pH adjustment of some samples. Visual detection was found to be about as sensitive as detection with a spectrophotometer, especially in milk-based matrices.
authors.affiliation: BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA.
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Dodge
authors.affiliation: School of Science and Technology, Universidad del Este, Carolina, Puerto Rico.
authors.forename: Kelvin
authors.initials: K
authors.lastname: Carrasquillo
authors.affiliation: School of Science and Technology, Universidad del Este, Carolina, Puerto Rico.
authors.forename: Luis
authors.initials: L
authors.lastname: Rivera
authors.affiliation: Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Xu
authors.affiliation: BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA.
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: Wackett
authors.affiliation: BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA Department of Soil, Water, and Climate, University of Minnesota, St. Paul, Minnesota, USA Sadowsky@umn.edu.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Sadowsky
mesh_terms: D000036:Abrin / Q000032:analysis*; D015415:Biomarkers / Q000032:analysis*; D003124:Colorimetry / Q000379:methods; D004798:Enzymes; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D064088:Hazard Analysis and Critical Control Points / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D026121:Indole Alkaloids / Q000032:analysis*; D010089:Oxidoreductases, N-Demethylating / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012680:Sensitivity and Specificity; D013997:Time Factors; D014368:Tryptophanase / Q000235:genetics / Q000378:metabolism
chemical_list: D015415:Biomarkers; D004798:Enzymes; D029968:Escherichia coli Proteins; D026121:Indole Alkaloids; D011994:Recombinant Proteins; D000036:Abrin; C102761:SolA protein, E coli; D010089:Oxidoreductases, N-Demethylating; D014368:Tryptophanase; C496492:abrine