Phenolphthalein Monophosphate as a Substrate for Serum Alkaline Phosphatase

Abstract

Abstract A rapid and precise procedure for serum alkaline phosphatase employs phenolphthalein monophosphate as the substrate. This compound is readily hydrolyzed and directly provides a chromogen for colorimetric determination. The color produced is linear with respect to both enzyme concentration and incubation time and is stable. Reagent and serum blanks are negligible. Various factors which affect alkaline phosphatase activity have been evaluated. The importance of the proper selection of buffer species, concentration, and pH is emphasized.