Evaluation of a New Continuous Colorimetric Method for Determination of Serum Pseudocholinesterase Catalytic Activity and its Application to a Centrifugal Fast Analyser

Abstract

The evaluation of a new commercially available assay system for the determination of serum pseudocholinesterase catalytic activity and its application to a kinetic analyzer was reported. The assay is based on the colorimetric method of Okabe et al. choline, liberated from benzoylcholine by pseudocholinesterase, is oxidized by choline oxidase (EC 1.1.3.17) to betaine with the simultaneous production of hydrogen peroxide, which oxidatively couples with 4-aminoantipyrine and phenol in the presence of peroxidase to yield a colored compound with maximal absorbance at 500 nm. The procedure not only has the advantage of being continuous, colorimetric and totally enzymatic but also appears to be precise (between-day analysis gives coefficient of variation between 3.5 and 5.6%) and accurate: the results obtained from normal and pathological sera [from humans] show excellent correlation with those obtained by the alternative procedures employing propionylthiocholine, acetylthiocholine and butyrylthiocholine as substrates.