A new method for the assay of purine metabolic enzymes.

Abstract
We have established new colorimetric methods for the assay of adenosine deaminase, purine nucleoside phosphorylase and guanase activities in serum, based on the formation of hydrogen peroxide with xanthine oxidase as a coupling enzyme. [chemical formula] The proposed methods were found to be precise and convenient. Under the assay conditions, the mean levels of adenosine deaminase, purine nucleoside phosphorylase and guanase activities in the sera of normal subjects were 5.8±2.2 I. U./1, 3.7±2.1 I. U./1 and 0.5±0.3 I. U./1, respectively.