ToxSci Advance Access originally published online on December 15, 2007
Toxicological Sciences 2008 102(2):425-432; doi:10.1093/toxsci/kfm304
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A Gene-Shuffled Glyphosate Acetyltransferase Protein from Bacillus licheniformis (GAT4601) Shows No Evidence of Allergenicity or Toxicity





* Pioneer Hi-Bred International, Inc., Johnston, Iowa 50131
Charles River Laboratories, Redfield, Arkansas 72132
DuPont Haskell Laboratory, Newark, Delaware 19714
DuPont Agriculture and Nutrition, Wilmington, Delaware 19880
¶ Pioneer Hi-Bred International, Inc., Verdia Campus, Redwood City, California 94063
|| Department of Pediatrics and Immunobiology, Mount Sinai School of Medicine, New York, New York 10029
||| Sungkyunkwan University School of Medicine, Seoul, Korea
1 To whom correspondence should be addressed at Pioneer Hi-Bred International, Inc., 7250 NW 62nd Ave., P.O. Box 552, Johnston, IA 50131-0552. Fax: (515) 334-4478. E-mail: bryan.delaney{at}pioneer.com.
Received October 10, 2007; accepted December 11, 2007
| Abstract |
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The glyphosate acetyltransferase (gat) gene from Bacillus licheniformis was subjected to multiple rounds of gene shuffling to optimize kinetics of corresponding GAT proteins to acetylate the herbicide active ingredient glyphosate. Genetically modified soybeans expressing the gat4601 gene (356043 soybeans) are tolerant to the application of glyphosate. The current manuscript reports the outcome of the allergenicity and toxicity assessment for the GAT4601 protein. Bioinformatic comparison of the amino acid sequence of GAT4601 did not identify similarities to known allergenic or toxic proteins. In vitro studies conducted with heterologously produced GAT4601 protein demonstrated that it was rapidly degraded in simulated gastric fluid containing pepsin (< 30 s) and in simulated intestinal fluid containing pancreatin (< 2 min) and completely inactivated at temperatures above 56°C. The GAT4601 protein expressed in planta is not glycosylated and similar protein profiles were observed in flour extracts from 356043 soybeans and nontransgenic near isoline comparator soybeans (Jack) using serum from soy allergic persons. No evidence of adverse effects was observed in mice following acute oral exposure to 2000 mg/kg of GAT4601 protein or in a repeated dose dietary exposure study at doses of 800–1000 mg/kg/day. This comprehensive assessment demonstrates that the GAT4601 protein does not present a risk for adverse effects in humans when used in the context of agricultural biotechnology.
Key Words: glyphosate acetyltransferase; bioinformatics; in vitro digestibility; allergenicity; toxicology; transgenic crop; gene shuffling.