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- Title
Evolution of a microbial acetyltransferase for modification of glyphosate: a novel tolerance strategy.
- Authors
Siehl, Daniel L.; Castle, Linda A.; Gorton, Rebecca; Yong Hong Chen; Bertain, Sean; Hyeon-Je Cho; Keenan, Robert; Lassner, Michael W.; Liu, Donglong
- Abstract
N-Acetylation is a modification of glyphosate that could potentially be used in transgenic crops, given a suitable acetyltransferase. Weak enzymatic activity (kcat = 5 min-1, KM = 1 mM) for N-acetylation of glyphosate was discovered in several strains of Bacillus licheniformis (Weigmann) Chester by screening a microbial collection with a mass spectrometric assay. The parental enzyme conferred no tolerance to glyphosate in any host when expressed as a transgene. Eleven iterations of DNA shuffling resulted in a 7000-fold improvement in catalytic efficiency (kcat/KM), sufficient for conferring robust tolerance to field rates of glyphosate in transgenic tobacco and maize. In terms of kcat/KM, the native enzyme exhibited weak activity (4-450% of that with glyphosate) with seven of the common amino acids. Evolution of the enzyme towards an improved kcat/KM for glyphosate resulted in increased activity toward aspartate (40-fold improved kcat), but activity with serine and phosphoserine almost completely vanished. No activity was observed among a broad sampling of nucleotides and antibiotics. Improved catalysis with glyphosate coincided with increased thermal stability.
- Subjects
ACETYLATION; ACYLATION; GLYPHOSATE; GLYCINE; HERBICIDES; TRANSGENIC plants; ACETYLTRANSFERASES; BACILLUS (Bacteria)
- Publication
Pest Management Science, 2005, Vol 61, Issue 3, p235
- ISSN
1526-498X
- Publication type
Article
- DOI
10.1002/ps.1014