The alkaline phosphatase from bone: transphosphorylating activity and kinetic mechanism.
For the purified alkaline phosphatase from bone, the ability to catalyze a phosphate transfer reaction from p-nitrophenyl phosphate to two different hydroxy acceptor compounds, ethanolamine and glycerol, was established by identification of the formed phosphorylated products, phosphoethanolamine and glycerol 3-phosphate, respectively. In addition, a steady-state kinetic analysis of the hydrolysis of p-nitrophenyl phosphate in the presence of an added nucleophile, diethanolamine, gave rise to the proposal of a simple model for the kinetic mechanism of the enzyme. This mechanism includes a covalent phosphoryl enzyme intermediate, the dephosphorylation of which by water (k3) or a nucleophile (k4) is rate-determining. According to this model, in the presence of diethanolamine, k3 and k4 were determined to be 4.44 s-1 M-1 and 1000 s-1 M-1, respectively. Therefore, in vitro a suitable nucleophile, such as diethanolamine, seems to be a better phosphate acceptor than water. These results may suggest that alkaline phosphatase from bone could be well suited for catalyzing phosphate transfer reactions in vivo as well.
Müller
K
K
Department of Dentistry, Karl-Marx-University, Leipzig, F.R.G.
Schellenberger
V
V
Borneleit
P
P
Treide
A
A
D000469:Alkaline Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001842:Bone and Bones / Q000201:enzymology*; D005994:Glycerophosphates / Q000032:analysis; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D010770:Phosphotransferases; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D005994:Glycerophosphates; C029620:alpha-glycerophosphoric acid; D010770:Phosphotransferases; D000469:Alkaline Phosphatase