332-6 Maleic-Itaconic Polymers As Urease Inhibitors.
See more from this Division: SSSA Division: Nutrient Management and Soil and Plant Analysis
See more from this Session: Nitrogen Efficiency, Cycling and Environmental Impacts
Wednesday, October 25, 2017: 9:15 AM
Tampa Convention Center, Room 10
Abstract:
Urea is the primary source of inorganic N soil fertilizer, and it must be hydrolyzed to yield a N source that can be assimilated by plants. The hydrolysis of urea is slow, but it is accelerated 1015-fold by urease, a nickel-dependent enzyme.[1] The urea hydrolysis determines an overall pH increase, causing significant ammonia volatilization that decreases the efficiency of urea-based fertilization. Therefore, a tight control of its activity is required for agronomic purposes. The chemistry of the enzyme and its inhibition has been elucidated in the past few years by our group,[1] through the structural characterization of urease bound to several classes of inhibitors, including sulfur compounds, boric acid, hydroxamic acids, organo-phosphorous compounds, carboxylic acids, quinones, catechols, and N-(n-butyl) thiophosphoric triamide (NBPT) [2].
Maleic-Itaconic polymers (MIPs) have been shown to decrease the N loss as ammonia volatilization.[3] In order to evaluate the possible inhibition effect of MIPs on urease activity, we performed a study using urease from jack bean (Canavalia ensiformis) at pH 7.5 and pH 5.0. The results indicate that MIPs do not inhibit urease at pH 7.5, confirming previous reports.[4] However, a strong urease inactivation is observed at pH 5.0. To elucidate the mechanism of urease inactivation by MIPs, their nickel sequestration capability was investigated. The data indicate that MIPs are able to extract the essential Ni(II) ions from the active site of urease, determining a complete and rapid inactivation of the enzyme, at pH 5.0. This pH-dependent behavior is consistent with a role of MIP in shifting the Ni(II)-urease dissociation equilibrium, following the protonation of the metal-coordinating histidine residues in the urease active site, through binding and chelation of the Ni(II) ions, and their incorporation in the polymer framework.
References
1. L. Mazzei, F. Musiani, and S. Ciurli – The Biological Chemistry of Nickel - RSC Metallobiology series, 2017, 60-97.
2. L. Mazzei, M. Cianci, U. Contaldo, F. Musiani, and S. Ciurli – Manuscript in preparation.
3. X. Peng, B. Maharjan, C. Yu, A. Su, V. Jin, R. B. Ferguson – Agron. J. 2015, 107, 871-879
4.R. J. Goos, Soil Sci. Soc. Am. J. (2013), 77, 1418.
Maleic-Itaconic polymers (MIPs) have been shown to decrease the N loss as ammonia volatilization.[3] In order to evaluate the possible inhibition effect of MIPs on urease activity, we performed a study using urease from jack bean (Canavalia ensiformis) at pH 7.5 and pH 5.0. The results indicate that MIPs do not inhibit urease at pH 7.5, confirming previous reports.[4] However, a strong urease inactivation is observed at pH 5.0. To elucidate the mechanism of urease inactivation by MIPs, their nickel sequestration capability was investigated. The data indicate that MIPs are able to extract the essential Ni(II) ions from the active site of urease, determining a complete and rapid inactivation of the enzyme, at pH 5.0. This pH-dependent behavior is consistent with a role of MIP in shifting the Ni(II)-urease dissociation equilibrium, following the protonation of the metal-coordinating histidine residues in the urease active site, through binding and chelation of the Ni(II) ions, and their incorporation in the polymer framework.
References
1. L. Mazzei, F. Musiani, and S. Ciurli – The Biological Chemistry of Nickel - RSC Metallobiology series, 2017, 60-97.
2. L. Mazzei, M. Cianci, U. Contaldo, F. Musiani, and S. Ciurli – Manuscript in preparation.
3. X. Peng, B. Maharjan, C. Yu, A. Su, V. Jin, R. B. Ferguson – Agron. J. 2015, 107, 871-879
4.R. J. Goos, Soil Sci. Soc. Am. J. (2013), 77, 1418.
See more from this Division: SSSA Division: Nutrient Management and Soil and Plant Analysis
See more from this Session: Nitrogen Efficiency, Cycling and Environmental Impacts