Abstract
Molinate is a recalcitrant thiocarbamate used to control grass weeds in rice fields. The recently described molinate hydrolase, from Gulosibacter molinativorax ON4T, plays a key role in the only known molinate degradation pathway ending in the formation of innocuous compounds. Here we report the crystal structure of recombinant molinate hydrolase at 2.27 Å. The structure reveals a homotetramer with a single mononuclear metal-dependent active site per monomer. The active site architecture shows similarities with other amidohydrolases and enables us to propose a general acid-base catalysis mechanism for molinate hydrolysis. Molinate hydrolase is unable to degrade bulkier thiocarbamate pesticides such as thiobencarb which is used mostly in rice crops. Using a structural-based approach, we were able to generate a mutant (Arg187Ala) that efficiently degrades thiobencarb. The engineered enzyme is suitable for the development of a broader thiocarbamate bioremediation system.
Highlights
Molinate (S-ethyl azepane-1-carbothioate) is one of the most intractable thiocarbamates [1] and is extensively used worldwide to control grass weeds in rice crops
There is only one described microbial system able to degrade molinate to innocuous compounds: a five strong bacteria consortium from which Gulosibacter molinativorax ON4T is responsible for the initial breakdown of the herbicide by cleaving its thioesther bond, releasing ethanethiol and azepane-1-carboxilate (ACA) [3, 4]
We demonstrate that molinate hydrolase is inhibited by ethanethiol, explaining the inhibition of Gulosibacter molinativorax ON4T growth when this molinate hydrolysis product accumulates
Summary
Molinate (S-ethyl azepane-1-carbothioate) is one of the most intractable thiocarbamates [1] and is extensively used worldwide to control grass weeds in rice crops. There is only one described microbial system able to degrade molinate to innocuous compounds: a five strong bacteria consortium from which Gulosibacter molinativorax ON4T is responsible for the initial breakdown of the herbicide by cleaving its thioesther bond, releasing ethanethiol and azepane-1-carboxilate (ACA) [3, 4]. This reaction is catalyzed by molinate hydrolase (MolA) [5]. For molinate concentrations over 2 mM and in the absence of other members of the bacterial consortium, PLOS ONE | DOI:10.1371/journal.pone.0123430 April 23, 2015
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
