[Determination of aryl esterase activity in the human serum using 4-nitrophenyl acetate]

A new determination of esterases and arylesterases (E. C. 3.1.1.2.) with 4-nitrophenylacetate is described. The results are compared with those of the method described by Pilz using phenylacetate. 4-nitrophenylacetate instead of phenylacetate allows a kinetic reaction. The precision of the determination is good, the method easy to handle. Normal values: 1100--2600 U/1 (total esterases), 700--2100 U/1 (arylesterases) at +25 degrees C.