[Use of inorganic pyrophosphatase as a marker in enzyme immunoassays]

A technique of heterogeneous enzyme immunoassay with the E. coli inorganic pyrophosphatase as marker enzyme and Malachite green dye and acidic molybdate as color reagent is developed. Color change (light-yellow/greenish blue) is extremely suitable for visual perception, in some cases making unnecessary the measuring device. Assays with pyrophosphatase are 5-10 times more sensitive than with peroxidase. Further advantages of pyrophosphatase include high thermostability, insensitivity to sodium azide, low value of Michaelis constant (5 microM), substrate stability. Examples are given of use of the pyrophosphatase for assays of human alpha-fetoprotein and immunoglobulin.