Polymer membrane ion-selective electrodes as a convenient tool for lipases and esterases assays

We have proposed a novel assay for lipases and esterases activity determination based on potentiometry with ion-selective electrodes (ISEs). Enzyme preparations, obtained from the living cells, are complex mixtures of various proteins, short peptides, lipids, carbohydrates, and other compounds. The most commonly used quantitative methods in enzyme studies are based on spectrophotometric or spectroflourimetric protocols which has significant limitations. They are not valid for samples that are turbid or strongly colored. To overcome those drawbacks we have proposed an assay based on potentiometry with ISEs for lipases and esterases activity determination. This electrochemical methodology represents an attractive tool for enzyme analysis, because of its low detection limit, independence from sample volume and from sample turbidity. The usefulness of this assay has been proven by the determination of the activity of various raw enzymes "acetone powders" isolated from animal tissues. Moreover, activities of fractions obtained during purification of one of those raw biocatalysts were also determined that way. The reliability of determination enzyme activity with ISE assay was proven by comparison with a classical spectrophotometric method.