Liang,Y. and Blake,R.E.(2009): Compound- and enzyme-specific phosphodiester hydrolysis mechanisms revealed by δ18O of dissolved inorganic phosphate: Implications for marine P cycling. Geochimica et Cosmochimica Acta, 73, 3782-3794.

『溶存無機燐酸塩のδ18Oから明らかにされた化合物および酵素固有のリン酸化ジエステルの加水分解メカニズム:海洋リン循環との関連』


Abstract
 We have studied the oxygen isotope signature of inorganic phosphate (Pi) generated by hydrolysis of nucleic acid phosphodiester (P-diester) compounds by cell-free enzymes (Deoxyribonuclease 1, Phosphodiesterase a, Alkaline phosphatase) and microbial cultures at natural isotopic abundances. We demonstrate that the diesterase-catalyzed hydrolytic step leads to incorporation of at least one water O into released Pi for a total of two O atoms from water incorporated into Pi released from P-diesters. In the presence of Phosphodiesterase a, 16O is preferentially incorporated into nucleotides released from DNA; whereas 18O is preferentially incorporated into nucleotides released from RNA. A strong consistency between predicted O-isotope regeneration signatures based on results of cell-free enzyme experiments and measured isotopic signatures from independent experiments with E. coli cultures was observed and confirms proposed models for phosphoester hydrolysis. Results from these studies made at natural 18O abundance levels provide a new tool, enzyme-specific O-isotope fractionation, for investigations of organophosphate metabolism and phosphorus cycling pathways in natural aquatic systems.』

1. Introduction
 1.1. Structure-reaction-based model for O-isotope effects of phosphoester hydrolysis
2. Materials and methods
 2.1. Cell-free enzymatic degradation experiments
 2.2. E. coli phosphodiester degradation experiments
 2.3. Analytical methods
3. Results
 3.1. Cell-free enzymatic DNA degradation experiments
 3.2. Cell-free enzymatic RNA degradation experiments
 3.3. E. coli phosphodiester degradation experiments
4. Discussion
 4.1. Cell-free DNA degradation experiments
 4.2. Cell-free RNA degradation experiments
 4.3. Parameter determination for the phosphoester hydrolysis model: O-isotope fractionation factors associated with diester bond cleavage
 4.4. Prediction of δ18O signatures of regenerated Pi
 4.5. Testing the phosphoester hydrolysis model using intact microbial cells: experiments with E. Coli
 4.6. Interpretation of measured DIP δ18O values from natural systems
5. Conclusions
Acknowledgment
References


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