Alkaline phosphatase catalyzes the phosphates hydrolysis and ester transfication under the presence of external alcohol. This enzyme contains two Zn(II) ion and one Mg(II) ion at the active site, and it is believed that the key intermediate Zn(II)-OH - is afforded by the deprotonation of the Zn(II)-bound water. While the metal hydroxy moiety can be the good candidate for the nucleophilic attack toward the ester, there is one serine residue adjacent to the Zn(II) ion and that amino acid residue may have a significant roll for the catalytic reaction in this enzyme. In the case of none-metal hydrolytic enzyme, such as chymotrypsin, the alcoholic OH in serine residue works as the nucleophile activated by an adjacent imidazole. The reaction of the activated serine in chymotrypsin with ester affords the acyl intermediate, finally the hydrolysis reaction of the acyl intermediate occurs by the external water. Therefore, as the roll of serine residue in alkaline phosphatase is not clear, the established reaction mechanism of alkaline phosphatase does not exist at the present stage.Kimura et. al. propose that the alcohol residue can be activated by the hydrogen bond with the Zn(II)-bound OH - at the active center to attack the substrate nucleophilically. Furthermore, it is proposed that the activated alcoholic OH can work as much stronger nucleophile than the metal-bound hydroxy moiety based on their model chemistry. That implies the ester transfication may also proceed in the same manner by use of external alcohol, instead of serine residue.Very recently we obtained the crystal structure of the dinuclear bis(Hydroxy)Ni(II) complex [TPANi(II)(μ-OH)Ni(II)TPA] 2 + (TPA = tris(pyridylmethyl)amine) (1). On the other hand, by the recrystallization of 1 in methanol, the crystal contains methanol in the cell and that methanol places close to the Ni(II)-bound hydroxy group. Furthermore, the bond length between the Nickel and oxygen in ligated hydroxy of this compound is longer than that of the structure without methanol. We concluded there was the hydrogen bond between the ligated hydroxy oxygen and alcohol in this structure, and that hydrogen bonding weakened the bond between the Nickel and hydroxy group. These data indicate the alcohol can form the adduct to the complex 1 via hydrogen bond potentially in the solution, too. That prompted us to investigate the reactivity of complex 1 toward ester under the presence of alcohol.The hydrolysis reaction of p-nitro phenyl acetate (PNPA) by complex 1 was performed and the rate of the reaction was estimated by the increase in 400 nm absorption derived from p-nitrophenolate in MeCN solution. It turned out that the reaction of 1 with PNPA under the presence of alcohol proceeded much faster than the reaction without alcohol. Furthermore, by adding the 20 equiv. of ethanol toward the complex 1 in this reaction with PNPA, we obtained ethyl acetate quantitatively toward the amount of hydroxy group in the complex 1. The ester transfer reaction by use of other inactive ester such as phenyl acetate could be also observed in this reaction system. We propose that the reactive intermediate of this ester transfer reaction is the activated hydroxy moiety in alcohol which has the hydrogen bond with the Ni(II)-bound OH group.