Phenolphthalein Monophosphate as a Substrate for Serum Alkaline Phosphatase

Abstract The procedure for serum alkaline phosphatase determination employing phenolphthalein monophosphate as substrate was evaluated under routine clinical laboratory conditions. A straight-line response to increasing serum concentration was observed, and the reaction was shown to be Mg++ dependent. The method proved to be extremely simple, and the results obtained correlated well with those given by a standard routine procedure involving determination of the liberated inorganic phosphate.