The last century saw the introduction of a host of anthropogenic compounds into the environment, such as herbicides, pesticides and antibiotics.  This influx of new compounds has introduced a range of new selection pressures such as toxicity and the availability of abundant nutrient sources.  Nature has evolved mechanisms to deal with these new selection pressures, including the development of new metabolic pathways.  These new metabolic pathways and their associated enzymes are a tremendous resource for advancing our understanding of the mechanisms and constraints that underpin the evolutionary process, particularly with respect to the acquisition of new enzymatic functions. The atrazine catabolism pathway from Pseudomonas sp. strain ADP is a particularly well studied example of a metabolic pathway that has evolved in response to the addition of man-made chemicals to the environment.  The pathway is comprised of six enzymatic steps: the sequential hydrolysis of chloride and two N-alkyl chains to produce cyanuric acid by AtzA, AtzB and AtzC; the subsequent ring opening of cyanuric acid by AtzD; and two deamination steps to complete mineralisation by AtzE and AtzF.  The enzymes that catalyse the first three steps of the pathway (AtzA, AtzB and AtzC) are likely to have recently evolved new substrate specificities as a response to the presence of atrazine in the environment. We have recently solved the structures of AtzA, AtzC, AtzD and AtzF, shown how substrates and inhibitors bind, determined the quaternary structures and looked at the activity changes of engineered mutations. AtzD is shown to be a novel fold derived from the trimerisation of a protein from the YgjF superfamily of enzymes and this three-fold symmetry extends down into the active site. Although these enzymes have been studied in depth for the last 20 years, these new structures add a tremendous amount of detailed information and have changed our perceptions of the enzymatic processes used to mineralise atrazine from the environment.