We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham e-Theses
You are in:

Plant carboxylesterases involved in pesticide hydrolysis

Gershater, Markus Christian (2006) Plant carboxylesterases involved in pesticide hydrolysis. Doctoral thesis, Durham University.



Many herbicides are applied in the form of carboxylic esters to increase their hydrophobicity and hence aid their passage through the waxy cuticle. Hydrolysis in planta of these pro-herbicide esters releases the active acid or alcohol and the rate of this cleavage can be a factor in determining herbicide selectivity. Protein extracts from 13 crop and weed species were assayed for carboxylesterase activity toward multiple xenobiotic and pesticide ester substrates, including 2,4-D-methyl, aryloxyphenoxypropionate esters and p-nitrophenyl esters. A diversity of activities was exhibited by the different species, with Arabidopsis thaliana extracts showing high hydrolytic activity toward several xenobiotic esters, particularly 2,4-D- methyl.The major 2,4-D-methyl hydrolysing enzyme in arabidopsis cell cultures was purified through three rounds of chromatography, then selectively labelled with a biotinylated fluorophosphonate probe (FP-biotin). Following streptavidin affinity purification, the labelled protein was identified by proteomics as the previously uncharacterised serine hydrolase AtCXE12. Recombinant AtCXE12 was subsequently confirmed to effectively hydrolyse 2,4-D-methyl.A T-DNA insertion knockout line that did not express AtCXE12 was identified and characterised. Protein from the knockout plants did not contain AtCXE12 and was found to have a reduced rate of 2,4-D-methyl hydrolysis compared to wild-type plant extracts. This translated into a higher tolerance of 2,4-D-methyl in young atcxel2 plants, due to a lower rate of bioactivation of the pro-herbicide.The fluorophosphonate-based chemical probe was subsequently used to identify other major serine hydrolases in arabidopsis. AtCXE12 and three previously uncharacterised hydrolases were identified, each belonging to a distinct enzyme family.

Item Type:Thesis (Doctoral)
Award:Doctor of Philosophy
Thesis Date:2006
Copyright:Copyright of this thesis is held by the author
Deposited On:09 Sep 2011 09:57

Social bookmarking: del.icio.usConnoteaBibSonomyCiteULikeFacebookTwitter