para-Nitrophenylphosphate


para-Nitrophenylphosphate (pNPP) is a chromogenic substrate for acid and alkaline phosphatase in ELISA and conventional spectrophotometric assays. These enzymes catalyse the hydrolysis of pNPP to yellow para-nitrophenol. This product absorbs strongly at 405 nm and can be measured with a visible light spectrophotometer.