Abstract
A sensitive assay method for adenosine deaminase activity in human serum is described based on the flow-injection determination of inosine formed enzymatically from substrate adenosine. Serum (10μl) is incubated with adenosine in the presence of urate oxidase and catalase, and the resulting mixture, after deproteinization with perchloric acid, is introduced into a flow-injection system in which immobilized enzyme columns of purine nucleoside phosphorylase, xanthine oxidase, urate oxidase and horseradish peroxidase are connected in series in that order in the flow line. Hydrogen peroxide formed in the enzymatic conversion of inosine is measured fluorimetrically by reaction with 3-(p-hydroxyphenyl) propionic acid in the system. The lower determinable limit of adenosine deaminase activity is 0.17 U/1 serum.
