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The action of EDTA on human alkaline phosphatases

1967; Elsevier BV; Volume: 139; Issue: 2 Linguagem: Inglês

10.1016/0005-2744(67)90040-x

1878-1454

R. A. J. Conyers, Donald Birkett, F. C. Neale, Solomon Posen, Joan Brudenell-Woods,

Enzyme function and inhibition

The effects of EDTA on the human alkaline phosphatases (orthophosphoric monoester phosphohydrolase, EC 3.1.3.1) of bone, intestine and placenta, have been studied by means of automated methods employing controlled concentration gradients. EDTA has three effects of these phosphatases: (a) In the presence of excess substrate, low concentrations of EDTA (10−5-10−3 M) cause a loss of phosphatase activity which is the same irrespective of the EDTA concentration. (b) Above 10−3 M EDTA bone and intestinal phosphatases display an increasing loss in activity with increasing concentrations of EDTA. Placental phosphatase, however, displays a progressive gain in activity with increasing concentration of EDTA. (c) Preincubation of the phosphatases with EDTA results in a time-dependent inactivation which is not reversed by dilution. This inactivation is also temperature-dependent and pH dependent. Alkaline phosphatases from different tissues show different susceptibilities to the irreversible inactivation by EDTA. The controlled concentration gradients were also used to study the kinetics of the action of EDTA on these phosphatases. Complex kinetics were observed with all alkaline phosphatases.