Enzymes for the biodegradation of s-triazines

s-Triazine rings are typically not found in nature but are commonly used in industry. Prominent industrial s-triazines are the herbicide atrazine and the polymer precursor melamine. Microorganisms have been identified that metabolize these and other s-triazine compounds via the common intermediate cyanuric acid, or 1,3,5-triazinane-2,4,6-trione. Cyanuric acid also forms from the spontaneous discharge of chlorine from di- and tri-chloroisocyanuric acids that are used for disinfection of water in pools, spas and fountains. All of the enzymes in atrazine, melamine and cyanuric acid metabolism have been purified, characterized, and studied with respect to their evolutionary origin. The enzyme cyanuric acid hydrolase is particularly interesting because it is a member of a rare protein family with a unique protein fold, as determined by X-ray crystallographic studies. The enzyme mechanism has been probed by site directed mutagenesis and X-ray crystallographic trapping of intermediates.  Commercially, cyanuric acid hydrolase is being tested for its potential to remove cyanuric acid from waters that have been disinfected with chlorinated cyanuric acids. To date, an immobilized form of the enzyme has been field tested for remediating waters containing cyanuric acid on ten thousand liter scale.