DEGRADATION OF METAL-NITRILOTRIACETATE COMPLEXES BY NITRILOTRIACETATEMONOOXYGENASE

Studies of metal-NTA complex degradation using NTA monooxygenase (NTA- Mo) can provide a mechanistic understanding of NTA degradation and lea d to approaches to remediate recalcitrant metal-NTA complexes (e.g., N iNTA(-)). NTA can exist in aqueous systems as various species dependin g upon the pH and types and concentrations of ions present (e.g., HNTA (2-), CaNTA(-) MgNTA(-)). An understanding of the aqueous speciation o f NTA is necessary to determine the substrate range of NTA complexes d egraded by MTA-Mo. The protonated form of NTA (HNTA(2-)) and CaNTA(-) were not degraded by NTA-Mo, while MgNTA(-), MnNTA(-), CoNTA(-), FeNTA (-), NiNTA(-), and ZnNTA(-) were degraded with similar K-m's. This is surprising because these metal-NTA complexes have different rates of b iodegradation by whole cells. This suggests that biodegradation of var ious metal-NTA complexes is limited by the rate of transport into the cell and that NTA-Mo may be useful for degrading metal-NTA complexes r ecalcitrant to degradation by whole cells. In mixed systems containing both substrate (MgNTA(-)) and nonsubstrate (CaNTA(-)), aqueous specia tion modeling was able to provide the substrate concentration, which c orrelated well with the rate data (r(2) = 0.95). This demonstrates tha t aqueous speciation modeling can be used to predict the rate of NTA d egradation by NTA-Mo for complex systems containing multiple species.