Magnesium ion is required for generating Ser102 nucleophile
Stec et al. suggested a reaction mechanism involving three metal ions, which is modified from the two metal ion catalysis theory proposed by Kim and Wyckoff (16). As mentioned, Ser102 acts as a nucleophile and facilitates the departure of an alcohol group during the first step of this reaction. In order for this occur, Ser102 has to be deprotonated. X-ray crystallography has been used to examine the mechanism of alkaline phosphatase. In this study, two new x-ray structures of AP in the presence and absence of inorganic phosphate were obtained and refined to 1.75 Å (9,16). By analyzing these new findings, clarification has been made regarding the activation of Ser102 and the requirement of magnesium ion in catalysis.
This theory states that magnesium ion binds to a water molecule, and this …show more content…
Three theories are presented and analyzed in this review. A recent study has refuted two past theories and concluded that magnesium contributes to transition state intermediate stabilization through a water ligand that forms a hydrogen bond with a charged oxygen atom. This is supported by a several notable observations. Zalatan et al. observed substantial effect on monoester hydrolysis and minimal effect on diester hydrolysis when a Mg(II) ion was removed. This evidence refutes the theory in which Mg(II) acting as general base because the activation of Ser102 nucleophile by Mg(II) is equally important for phosphate monoester and diester. In addition, if Mg(II) stabilizes the enzyme-phosphate structure by modulating Zn(II) ions, no significant effects should be obtained for phosphate diester and sulfate monoester while having large impact for phosphate monoester because it has more negative charges. However, these results also disagree with this model because a significant decrease in rate constant are seen on both phosphate and sulfate
Stec et al. suggested a reaction mechanism involving three metal ions, which is modified from the two metal ion catalysis theory proposed by Kim and Wyckoff (16). As mentioned, Ser102 acts as a nucleophile and facilitates the departure of an alcohol group during the first step of this reaction. In order for this occur, Ser102 has to be deprotonated. X-ray crystallography has been used to examine the mechanism of alkaline phosphatase. In this study, two new x-ray structures of AP in the presence and absence of inorganic phosphate were obtained and refined to 1.75 Å (9,16). By analyzing these new findings, clarification has been made regarding the activation of Ser102 and the requirement of magnesium ion in catalysis.
This theory states that magnesium ion binds to a water molecule, and this …show more content…
Three theories are presented and analyzed in this review. A recent study has refuted two past theories and concluded that magnesium contributes to transition state intermediate stabilization through a water ligand that forms a hydrogen bond with a charged oxygen atom. This is supported by a several notable observations. Zalatan et al. observed substantial effect on monoester hydrolysis and minimal effect on diester hydrolysis when a Mg(II) ion was removed. This evidence refutes the theory in which Mg(II) acting as general base because the activation of Ser102 nucleophile by Mg(II) is equally important for phosphate monoester and diester. In addition, if Mg(II) stabilizes the enzyme-phosphate structure by modulating Zn(II) ions, no significant effects should be obtained for phosphate diester and sulfate monoester while having large impact for phosphate monoester because it has more negative charges. However, these results also disagree with this model because a significant decrease in rate constant are seen on both phosphate and sulfate