Pseudomonas is a common soil bacterium that can use the abundant herbicide atrazine as a nitrogen source. Earlier this year we revised the Pseudomonas catabolic pathway for atrazine degradation after careful structural and biochemical analysis of the enzyme AtzE. In the process we discovered two new small proteins in an operon needed for the pathway (the cyanuric acid catabolism operon). One of the new proteins, AtzG formed a complex with AtzE - without which AtzE was insoluble and non-functional.
In Lygie Esquirol's third paper for the year (well done Lygie!), we show evidence that the second new protein, AtzH, is an enzyme. AtzH likely catalyses a step in the pathway that we hadn't previously known about, but which was revealed by our recent revision of the pathway. With this new work, we believe that we now have a complete understanding of the biochemical pathway used by this soil bacterium to degrade atrazine and we've gained some additional insight into the evolutionary steps taken during the assembly of the atz pathway.