Use of inhibited enzyme electrode for estimation of PEA diamine oxidase inhibitors

Abstract

A biosensor consisting of a Clark type oxygen electrode and immobilized pea diamine oxidase makes it possible amperometrically to quantify, on the basis of an inhibition effect, substrate analogues of the enzyme (aliphatic amino ketones and monoamines, aromatic diamines), some alkaloids (cinchonine, lobeline, norsedamine) and drugs (1-phenylcyclopropylamine, naphazoline). The output current signal of the inhibited bioelectrode is influenced by the thickness of the membrane and its enzyme content as well as by the sort of the substrate and oxygen concentration in the reaction medium. With most of the tested substances, the response time τ90 is 20-100 s and the linear concentration range about 10-6-10-3 mol l-1 can be observed. The inhibitor concentrations causing a change of the initial current by 50% correspond mostly to the published values of inhibition constants for soluble enzyme. The most efficient inhibitor of the pea diamine oxidase is 1,5-diamino-3-pentanone, for which the accuracy of the method was 5.6%, its reproducibility 7.2%, and detection limit 5 . 10-9 mol l-1.