Determination of acid phosphatase in biological fluids using a new substrate, 2,6-dichloro-4-nitrophenyl phosphate.

A new substrate, 2,6-dichloro-4-nitrophenyl phosphate (DCNP-P), is used for the determination of acid phosphatase (EC 3.1.3.2) in serum and urine. It was hydrolyzed by acid phosphatase to 2,6-dichloro-4-nitrophenol (DCNP) and phosphoric acid. At a pH of 4.5-6.0, the absorption of DCNP liberated by acid phosphatase was much higher than that of p-nitrophenol, which is commonly used as an aglycone in the acid phosphatase assay. By using DCNP-P as a substrate for acid phosphatase activity, determinations can be made without the colour reaction which requires the addition of an alkaline solution, and can be determined by the rate assay that does not require measurement of sample blanks in serum or urine. This method using DCNP-P is highly sensitive and is the most suitable for the rate assay of acid phosphatase activity in biological fluids.