The Possible Significance of Hexosephosphoric Esters in Ossification

Abstract

The activity of the bone phosphatase increases with alkalinity up to p h 9.4, but above 8.4 this is offset by the gradual inactivation of the enzyme. In the body, the optimum p H may be taken as about 8.4. The activity-p H curve has the form of the dissociation curve of a weak acid, P h about 8.2, or the dissociation-residue curve of a weak base. Variations in the concentration of the substrate between 0.003 M and 0.3 M do not affect the initial rate of hydrolysis. The rate of hydrolysis of glycerophosphpric ester is greatly retarded by inorganic phosphate in low concentrations, but glycerol (a 2nd hydrolysis product) in low concentration has no such effect. In high concentrations of glycerol and in presence of inorganic phosphate, synthesis of phosphoric ester takes place. Similar synthetic action of the enzyme has also been shown with mannitol, glycol, glucose, and fructose. Adrenaline, pltuitrin or thyroid have no effect on rate of hydrolysis or optimum p n of the enzyme. Action of the enzyme on various types of phosphoric ester is discussed.